John T. Andrews - US grants

Funds are requested for the purchase of a fathometer system suitable for installation on a small research boat. The fathometer is to be used for research by members of the Institute of Arctic and Alpine Research at the University of Colorado, Boulder. The equipment will be employed to conduct surveys of sediment thickness and sediment stratigraphy in lakes and shallow-marine environments prior to taking core samples of the sediments. Analysis of sediment cores from lakes and shallow- marine locations has proven very useful in the interpretation of global changes in climate and biosphere activity during the most recent geological past, and such reconstructions are vital for predicting future global climatic trends.

Controversy exists on the position of sea level along the NE margin of the Laurentide Ice Sheet between 10 and 18 ka. In addition, there are minimal constraints on the location of the ice front prior to the first mappable Late Pleistocene raised marine sediments date 10.7 ka. This research involves a detailed study of Late Quaternary sea level oscillations along the margin of the Laurentide Ice Sheet in the vicinity of Hudson Strait and Frobisher Bay, Arctic Canada. Previous field work suggested that significant oscillations of sea level occured over short intervals of time but these are difficult to resolve if one relies on dating shells in raised marine wediments. Using the "isolation" method for reconstructing detailed relative sea level curves, an approach which consists of coring a series of small lakes above the marine limit down to present sea level, changes in relative sea level and the paleoenvironments will be deduced from changes in diatom floras. Radiocarbon dating of small segments of cores close to transitions will be carried out by accelerator dating methods. As lakes will be cored beyond the 10.7 ka ice margin a focus of the research will be assessment of glacial/climate/sea level events across the Younger Dryas chron (ca 11-10ka). The subsequent period, between 8 and 10ka, was one of rapid ice sheet retreat and collapse and thus will serve as an analog for the hypothesized CO2 induced retreat of the West Antarctic Ice Sheet.

The effects of the sediment and meltwater fluxes from the Laurentide Ice Sheet on the North Atlantic are greatest where these are concentrated for reasons of ice sheet dynamics and/or topography. Detailed isotope stratigraphy, combined with AMS 14C dating, shows that the transition from glacial to interglacial conditions contains significant irregularities, e.g.the Younger Dryas stadial event. This award will continue amulti-parameter investigation of cryosphere/ocean interactions at the margin of the Hudson Strait ice stream. The study focuses on a suite of cores from 1000 to 2000 meters in the northwestern Labrador Basin. Methods include: detailed AMS dating, stable isotopic and sedimentological analyses, with the aim of documenting meltwater and sediment fluxes from the ice sheet, and into the North Atlantic Ocean. The cores can be placed in a firm stratigraphic context because of the availability of high-resolution Huntec acoustic records.

The investigations will continue investigation of the interactions between: 1) glacial response, 2) sea-level variations, and 3) climate, around the margin of the Laurentide Ice Sheet (LIS) in the vicinity of Hudson Strait and Frobisher Bay, Eastern Canadian Arctic. The time-scale for the investigation includes two major moraine forming intervals, the Hall and Frobisher Bay moraines, that are C-14 dated at >=10.3 and ca. 8.4 ka respectively. The former may be coeval with the Younger Dryas stadial of NW Europe; the latter is a major event (Cockburn Substage) around the residual Laurentide Ice Sheet. In the first year, 1987, we cored three lakes a few kilometers form the Terra Nivea Ice Cap, on the south side of Frobisher Bay, and distal to the Frobisher Bay moraines. In 1988 three lakes were cored distal to the Hall moraines. These lakes were cored at or below the marine limit so that we could 1) date the marine/freshwater transition for sea-level studies; and 2) use the litho-stratigraphy and diatom assemblages to investigate whether sea-level fell monotonically after deglaciation or if later transgressions occurred. Early studies by INSTAAR had suggested sea level fell rapidly after 9 ka ago unlike the more gradual emergence history farther north on Baffin Island. Stratigraphic sections in raised marine deposits indicated a possible transgression ca 8 ka ago. In cooperation with the AMS C-14 facility, University of Arizona, we have dated two of the marine/freshwater transitions in the first area; both date ca. 8.6 +/- ka despite a difference in elevation of 24 m. The emphasis in this renewal is to continue our program of lake coring in the region that lies distal to the 10.3 ka Hall moraines, but proximal to deposits of the Loks Land aminozone that has an estimated age of 40-50 ka. Numerous lakes exist in the area and are accessible for both winter and summer coring operations.

This award supports the establishment of a Working Group for the Paleoclimate of Arctic Lakes and Estuaries (PALE) initiative as part of Arctic Systems Science (ARCSS). The Working Group will develop a science and management plan for this program and will be active in its implementation.

This award will support an interaction between: 1) glacial response, 2) sea-level variations, and 3) climate, around the margin of the Laurentide Ice Sheet in the vicinity of Hudson Strait and Frobisher Bay, Eastern Canadian Arctic. The focus for the investigation includes two major moraine forming intervals, the Hall and Frobisher Bay moraines, that are C-14 dated at greater than 10.3 and ca. 8.4 thousands years respectively. The former may be coeval with the Younger Dryas stadial of NW Europe; the latter is a major event (Cockburn Substage) around the residual Laurentide Ice Sheet. Studies on mass physical properties, texture, pollen, and diatoms will be undertaken on a series of lake cores. One of the critical problems in arctic lake studies is C-14 dating of sediments with very low organic contents. This problem will be investigated by: 1) comparisons between AMS dates on macrofossils and bulk sediment dates; and 2) studies to document the C-14 inventory of two small lake basins which include sampling soils, raised marine sediments, water, and lake sediments.

The demonstration of a major advance from a Labradorean dispersal center flowing essentially at right angles to regional topographic features, and that overtopped Loks Land despite an unconstrained margin facing the open ocean to the SE, provides strong evidence that the flux of ice during this advance must have been great. The cross-sectional area for that portion of the ice facing the Labrador Sea is ca. 300 km2. Assuming a velocity between that of Jacobshavn Glacier, an outlet glacier draining the Greenland Ice Sheet (8 km a-1), and the Ross Ice Shelf, Antarctica (1 km a-1) yields an annual flux of 300 to 2400 km3 a-1. This is about the same fresh-water flux entering the North Atlantic when the St Lawrence outlet was opened by the retreating Laurentide Ice Sheet 11,000 years ago (30,000 m3 sec-1 or 1000 km3 a-1; Teller, 1988). Recognizing the importance of ice-sheet/ocean interactions in the global climate system, we are proposing a research campaign to include a new field effort to define more precisely the spatial limits of this newly recognized advance, and the timing of its onset and retreat, and to model the ice dynamics based on the field evidence. Specifically, we intend to address five objectives: 1) Defining the maximum limits of the Labradorean advance; 2) Deciphering the interaction between the Foxe outlet glacier the flowed out Frobisher Bay and the Labradorean ice sheet backfilling the bay; 3) Determining whether all of Meta Incognita Peninsula was over-ridden by Labradorean ice; 4) Defining the temporal limits of these advances; and using the field evidence on the limits and timing of ice sheet advance and retreat as input to glaciological models to provide realistic ice limits, and ice velocities. Accurate reconstructions of the overall configuration of the Laurentide Ice Sheet and the pattern of its flow are necessary to understand the climate and general circulation during a glaciation, the response of the earth's crust to loading, and contribute to our understanding of ice dynamics.

This award supports marine geologic research to document sediment flux and accumulation on the proximal (fjord/shelf) environments off Kangerdlugssuaq Fjord, East Greenland, and to compare these with similar shelf/fjord environments along the Eastern Canadian Arctic margin and with margins of the Nordic Seas (as part of the international PONAM Project). This research will emphasize the study of present-day sediment processes and fluxes within this fjord and will develop a model of variations in sediment fluxes and physical and biological composition since the late glacial. This work will also emphasize the paleoceanographic and paleoclimatic variations with time. The research will target opal and diatom flux as well as benthic foraminifera as indicators of change in surface water productivity and bottom water conditions. A reconnaissance cruise to the fjord and inner shelf in the autumn 1991, on an Icelandic research vessel, will provide preliminary data regarding the sea floor morphology, shallow seismic structure, surface sediment characteristics, bio- and lithostratigraphy, sedimentology, stratigraphy, hydrology and suspended matter. A second cruise, on the Canadian research vessel Hudson, in 1992 will obtain side- scan sonar data, additional high-resolution Huntec DTS stratigraphy of the fjord basin, and long cores that will allow further delineation of the relationships between the seismic and core stratigraphy.

This award is in support of one element of the PALE activity (Paleoclimates from Arctic Lakes and Estuaries). Research is focused on a lake coring program in the Eastern Canadian Arctic with the goal of recovering continuous records of environmental change for the last 10 to 15 thousand years. Baffin Island lies in a key location and analyses of climatic data indicate that this region serves as a bellwether for the circum-arctic climate system. This project will reconstruct past climates from down- core changes in the pollen and diatom assemblages, stable isotopic ratios and physical characteristic of the sediment in cores. The lakes will be strategically located along a N/S temperature transect, and across the E/W marine/continental climate gradient. Cores form these lakes will allow examination of questions related to climate change, including regional glacial history (timing and extent of the last continental ice advance and the pattern of deglaciation), sea level change (both postglacial emergence and the more recent submergence), and renewed development of cirque and mountain glaciers in the late Holocene (Neoglaciation). Sampling will be undertaken with a density commensurate with PALE objectives, i.e. decadal to centuries resolution depending on the accumulation rates within the different lake basins.

This award is in support of a one year standard grant to investigate ice ocean interactions during the late Quaternary in the Hudson Strait region of the northwest North Atlantic, which is the major sediment and meltwater route for deglaciation of the Laurentide Ice Sheet. Sediment cores will be obtained during a 1992 cruise to Hudson Strait and Frobisher Bay and these will be analyzed for: 1) carbon-14 of foraminifera, 20 stable oxygen and carbon isotopes of planktonic and benthic foraminifera, 3) down core mineralogy, and 4) changes in foraminifera species

This award supports paleoclimate reserch in Iceland within the framework of PALE (Paleoclimates of Arctic Lakes and Estuaries). Iceland occupies a key position in the North Atlantic in terms of both climatic and oceanographic parameters. The climate of the island is a function of the strength and location of the Icelandic Low, the strength and character of the freshwater outflow from the Arctic Basin, and the location of the North Atlantic Drift. These variables interact to affect the vegetation, hydrology, and glacial history of this area; Iceland thus well placed for developing longer proxy records of climate change.

9224254 Andrews This award supports a program to study sediment cores from the inner continental shelf and fjords of East Greenland. The goals are to determine paleoclimatic conditions and to understand ice- sheet ocean interactions during the late Quaternary. The project will use oxygen isotopes, carbon-14 ages, benthic foraminifera, and sediment provenance studies to develop a high resolution history of the paleoenvironmental conditions in the region. This project will develop information about the extent and duration of sea ice cover on the inner continental shelf of East Greenland during the late Quaternary and about discharge of freshwater from melting of land based ice in the Arctic Basin. The results of this work should be useful to help constrain models of climate change that are being developed from the Greenland Ice Sheet Project (GISP) ice core. ***

This award supports a program to study sediment cores from the Hudson Strait, which is widely believed to have been the drainage path for a major part of the Laurentide Ice Sheet. The goals are to understand the dynamic processes associated with the last stages of collapse of this marine based ice sheet. The project will use oxygen isotopes, carbon-14 ages, benthic foraminifera, and sediment provenance studies to develop a history of the changing paleoenvironmental conditions during the time that the Laurentide Ice Sheet was deteriorating.

9321135 Andrews This award is for support for a study to continue development of a chronology, reconstruct paleoenvironments, and understand the processes associated with major ice sheet instability (Heinrich events) of the eastern sector of the Laurentide Ice Sheet over the last glacial cycle. During the continental glaciation of North America, Hudson Strait drained a quarter to a third of the Laurentide Ice Sheet and was the major conduit for the transport of water, sediment, and icebergs from the ice sheet into the North Atlantic. The fluxes of these materials into the Labrador Sea and North Atlantic would have had a dramatic effect on the global climate system. A number of cores have been identified for study that will provide high-resolution records of ice sheet (Heinrich) events on centuries to decadal time scales. ***

9320217 Andrews This award is for support for graduate students to attend the annual Arctic Workshop and supports registration, housing and meals for approximately 25 students. These workshops have been held since 1972 and alternate their location between Boulder, Colorado and another location, every other year. The workshops will be held in Boulder in 1994 and 1996 and in Laval, Quebec, Canada in 1995. These workshops provide a vital forum for the exchange of ideas and data within the Arctic research community, at both the national and international level. ***

This project deals with the paleoclimate of the region that extends from the Eastern Canadian Arctic eastward to Greenland and Iceland. This is an area that is critical for the integration of present and past records of climatic change, especially within the context of the Arctic System Science Program (ARCSS research agenda. The main objectives of the research will be to concentrate on the evaluation, synthesis and interpetation of: i) instrumental records; ii) historical data sources from Iceland; iii) the GISP2 isotopic time-series; iv) high-resolution marine series near East Greenland; and v) annually laminated lake records from Southeast Baffin Island and Iceland. The project will include an analysis of climate impact in Iceland in recent centuries. Thus, although focussing on paleoclimatic reconstruction and interpretation, the research also has a human dimensions perspective and links directly with the needs of the new ARCSS Paleo initiative (Archeology and Ethnohistory) regarding the documentation and understanding of the role of climatic variations in the Norse expansion throughout the North Atlantic, and human responses to the so- called "Medieval Warm Period" and Little Ice Age". In conlcusion, the overall goal is directed towards improving the understanding of annual to century timescale fluctuations of climate in this region, as well as the influences of such changes on Humankind.

Abstract ATM-9520807 Andrews, John T. University of Colorado Title: Decadal-Scale Proxy Records of the Last 3,000 Years from the Eastern Canadian Arctic and Iceland Based on Lake Sediment and Palynology This PALE/ARCSS award supports a study of decadal-scale variability in the paleoclimate of Iceland over the last 3,000 years. It is specifically intended to unite projects of Baffin Island and Iceland by creating lake sediment and pollen records for Iceland that can be compared to similar high-resolution records from sites on Baffin Island, N.W.T., Canada. This effort will help to integrate paleoclimate records from Greenland, Iceland and the Eastern Canadian Arctic and will provide information useful in piecing together the synoptic climatology of the northern Atlantic region.

Abstract ATM-9503279 Miller, Gifford University of Colorado Title: Paleoclimate Records from Lake Sediment in a Cape Dyer- Quvitu Transect, Eastern Baffin Island, Arctic Canada The sensitivity of the polar regions to increased greenhouse gases is described by global circulation models. Rapid changes in Arctic boundary conditions that influence climate, such as vegetation type (especially tundra vs boreal forest), extent and duration of sea ice and seasonal snow cover, and continental ice thickness/ice berg discharge may have had dramatic impacts outside the Arctic in the past, and may have similar future impacts. These impacts underlie current interest in the role of the Arctic in the global climate system. A primary objective of the PALE Initiative (Paleoclimate from Arctic Lakes and Estuaries) is to obtain and analyze a series of lake sediment cores that span the circum-arctic region. This project focuses on the 0-20,000 yr time period, with opportunistic sampling of older records and high-resolution younger records where encountered. Research will continue lake-coring research efforts, including the interpretation of pollen, diatom, sedimentological and isotopic analyses. Work also continues to develop additional proxies for past climate utilizing the isotopic composition (C- and O- isotopes) of aquatic macrofossils and specific classes of dissolved organic matter preserved in lake sediments and changes in diatom floral assemblages.

Abstract ATM-9531397 Andrews, John University of Colorado, Boulder Title: Paleoclimate (0 to >14 ka) of W and NW Iceland, A Comparison of Lake and Near-Shore Marine Proxy Records: A USA/Iceland Contribution to P.A.L.E. Iceland is located on the eastern side of Denmark Strait in a region where changes in the extent and duration of sea ice have major impacts on both the marine and terrestrial environments. This area monitors the relative strength of both the northward advection of Atlantic Water and the southward flux of sea ice and freshwater in the East Greenland Current. This PALE/ARCSS award supports the recovery of a series of sediment cores from lakes in NW Iceland and compares their proxy records of climate with proxy records from marine cores taken from fjords and shelf-troughs off northwestern Iceland. Based on earlier PALE studies, decadal/centennial sampling resolution is realistic in both environments, and correlations within systems and between lakes and the offshore are enhanced by an abundance of regional tephras. A major Icelandic contribution to the grant will include ship-time to carry out coring along three fjord shelf transects in northwestern Iceland.

Funding is requested to support research on sediment cores obtained from eastern Greenland during a joint USA/Norwegian research cruise. The objectives of the proposal are to: 1) Document ice sheet/slope/deep-sea sediment transfers and interactions for the East Greenland/Denmark Strait margin over the last 30ka; 2) Test different hypotheses for the extent of the East Greenland ice sheet's margin during the Last Glacial Maximum (LGM) and the timing of retreat; and 3) Develop and interpret high-resolution marine records (decadal to centuries time-scales) of changes in the character of the surface water (East Greenland Current) and bottom water (Arctic Intermediate Water) over at least the last 14ka, and how these data reflect paleoceanogrphic changes in the Arctic and North Atlantic Oceans. The core on the shelf and slope are firmly placed in a seismic stratigraphic framework both from previous surveys and during core collection in 1996. The choice of the core sites was designed to 1) test two contrasting models for the extent of glacial ice on the south-central east Greenland margin during and since the LGM and to 2) investigate the paleoceanography and ice-sheet/ocean interactions across the Denmark Strait "gateway" between the Arctic and the North Atlantic over the interval of record (the last 30 ka). The extent of the East Greenland ice margin flanking Denmark Strait during the last glaciation is virtually unknown, yet this extent and the timing of deglaciation are important parameters for understanding the past changes in ocean circulation through the Denmark Strait, and the role of this ice margin in Heinrich events, meltwater spikes, and other abrupt climate changes during the glacial period. The research thrust for the Holocene is to document paleoceanographic and glacial conditions in the fjords and on the shelf, and to compare these reconstructions with other paleoclimate data such as the ( 18( record from Renland ice core, and the "Little Ice Age" events under study from the t errestrial neoglacial record. The results of these studies will help us to understand how, why, and how quickly the environment has changed in this region during the Holocene.

ABSTRACT OPP-9726510 OPP-9726417 OGILVIE, ASTRID ROGERS, JEFFREY UNIVERSITY OFCOLORADO OHIO STATE UNIVERSITY The project will examine the relationship between changing climatic conditions in the vicinity of Iceland and the abundance of Atlantic cod for the past 1000 years. The combination of climate and fisheries records will be used to determine possible impacts of climate-induced changes in cod fisheries on human populations. Of particular importance will be an examination of the societal response to climate change and fisheries abundance during two of the most dramatic climate events to occur in the North Atlantic region during recorded history, the "Little Ice Age" and the "Medieval Warm Period". The research will involve an interdisciplinary approach in which physical, climate, historical, and sociological evidence is gathered to examine effects of significant changes in the environment on human populations that depend on resources controlled in part by climate-driven systems. Therefore, the project will make a significant contribution to the determination of the human dimensions of global change in the North Atlantic during two periods of significant climate fluctuations.

This ESH award will support participation in an international coring cruise on the Marion Dufresne to collect high-resolution cores from both sides of the Denmark Strait in the North Atlantic. The cores will be anlayzed fro numerous sedimentological parameters (including stable isotopes and assemblages of planktic and benthic foraminifera and rock magnetics) to reconstruct the local variability of sea ice and land/ocean interactions during the Holocene and the late Pleistocene at decadal to centennial time scales.

Abstract
OPP-99-06812
Farmer

The Principal Investigators will use neodymiun, strontium, and lead isotopic data, and clay-silt mineralogy from glacial marine sediments in the NW Atlantic Ocean to study Laurentide and Greenland ice sheet dynamics on time-scales of the last full glacial cycle. Their basic premise is that the mineralogic and isotopic compositions of the less than 65 micron fraction from glacial marine will allow them to reconstruct the extent of the various ice sheets and their internal dynamics.

The project consists of two main parts. First, they will determine the isotopic and mineralogic character of fine-grained glacial sediments delivered to the marine environment at various "point" sources of icebergs in Baffin Bay and the Labrador Sea. Samples for the point source characterizations exist within their present core and surface sediment sample collections, or are available from the Core Repository Facility at Geological Survey of Canada. These data are critical for downcore studies of glacial sediment provenance because they will indicate if 1) sediments derived from a given portion of the ice sheets are mineralogically and isotopically distinct, and 2) if each iceberg source has provided isotopically and mineralogically homogeneous sediment. These characteristics must be established before any attempt to reconstruct ice sheet dynamics from sediment provenance studies can be attempted.

In the second part, the Principal Investigators will undertake specific downcore studies on three existing cores to determine changes in sediment provenance, style of deposition, phasing of ice sheet reactions, and ice sheet/ocean interactions. These cores have been selected along the iceberg transport trajectory and should show increasingly complex mixtures of sediment from different source regions. The cores selected are from northern Baffin Bay (HU77029-006), from a site east of the mouth of Hudson Strait (HU97048-007), and, south, from Cartwright Saddle on the central Labrador shelf (HU87033-017). Their analyses will concentrate on H139704S-007 because it is a new core. They will expand the chronological control by obtaining additional radiocarbon dates and undertake a full suite of sedimentological, foraminiferal, stable isotopic, and provenance studies. This will enable them to compare data in this core with data from present studies and to compare downcore mineralogic and isotopic variations to those of the glacial "point" sources. This comparison should provide new insights into changes in the extent, configurations, and dynamics of ice sheets around the NW Atlantic over the past 50 thousand years.

Abstract
OPP-0082347


The Principal Investigators will conduct a detailed study of high resolution IMAGES (International Marine Global Change Study) cores from the East Greenland continental shelf. Cores up to 25 m long were collected from specially targeted, high-resolution sites with support from a an NSF grant their partnership in the 1999 international IMAGES V cruise, Legs 3 and 4 in the Nordic Seas. The Leg 4 Greenland cores were collected for study of climate and glacial history of the shelf from degradation to the present. The sites were selected from seismic profiles and shorter gravity cores collected on previous. The 25 meter, high resolution cores are unprecedented in this are and likely represent at most the last 14,000 years. Initial radiocarbon and dating results and previous work indicate that the Principal Investigators will be able to resolve changes occurring on decade-to-century time scales. These records will provide an excellent basis for looking at the natural variability of sea ice and climate in the Arctic under a wide range of environmental conditions. The goal is to document the hydrography of the East Greenland Current, including its sea-ice cover and freshwater flux, and associated changes in the extent of the Greenland Ice Sheet and local glaciers during three critical time intervals. They will employ multiple proxies that have been calibrated to modem oceanographic, biological and sedimentological data. The proxies include: oxygen and carbon stable isotope analysis of benthic and planktonic foraminifers, benthic and planktic foraminiferal assemblages, grain-size changes (including quantification of iceberg rafted grains), carbon and carbonate flux changes, diatom assemblages and abundances lithofacies and paleomagnetic intensity records. The Principal Investigators will employ sampling intervals to provide decade to-century scale resolution of the environmental changes that have occurred through the critical time periods. These cores from a shelf area directly influenced by the arctic sea ice, rapid sedimentation rates and little influence of relative sea-level fluctuations offer exciting prospects for understanding natural variability in the Arctic sea ice, in the properties of the EGC, and in the interplay of paleoceanography, glacial history and paleoclimate.

0118455
Farmer

This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports a collaborative research project to study glacio-marine sediments from the Ross Sea toward an understanding of the history of the West Antarctic Ice Sheet (WAIS). Reliable predictions of the future response of the WAIS to changing climate and rising sea level depend, to a large extent, on improving our knowledge and understanding of its ice dynamics during the last glacial maximum (~18,000 yrs ago). Sediments from the Ross Sea, Antarctica, contain a detailed physical record that can be used to reconstruct past glacier flow patterns. Although significant progress has been made in constraining the extent of ice and the timing of its maximum extent, reconstructions of ice flow paths vary substantially. Studies have predicted that ice streams (regions of fast flowing ice) derived primarily from West Antarctica were dominant features of the Ross Ice Sheet, whereas an ice sheet modeling reconstruction showed roughly equal input from East and West Antarctic ice. Fundamental differences in rock types and ages beneath these source areas should allow the provenance of tills across the Ross Sea to be determined, facilitating the reconstruction of past ice flow paths. Thus the Ross Embayment provides an exciting opportunity to relate modern ice flow dynamics to past ice sheet dynamics and deposits.

A detailed provenance study of sediment collected in cores taken from across the Ross Sea floor will be carried out by linking the mineralogical, geochemical, and isotopic characteristics of the sediments from these cores to reference sediments collected from the probable source areas. From these data, the patterns of ice flow across the shelf can be constrained for the last glacial maximum. For this study, existing samples collected from the Ross Sea, and the source areas of East and West Antarctica will be utilized. Composition of the till deposited during the last ice advance will be characterized by examining the sand and pebble size fraction of the sediment, the clay mineralogy, elemental abundance and samarium-neodymium (Sm-Nd) isotopic composition of the silt and clay size fraction. The source of silt and clay fraction may be problematic because of possible mixing of continental and marine sources. This problem will be addressed by determining the composition of modern marine samples which can then be 'subtracted' from the till composition.

Samples from the source areas will be analyzed first to determine the compositional fingerprint of each area. Ice flow paths will be determined based on the correspondence between the source areas and the measured values across the Ross Sea. The goal of this project is to characterize both lateral and vertical variations in diagnostic aspects of till mineralogy and isotopic composition in order to make a significant contribution to the understanding of changes in ice sheet dynamics on time scale of the past 30,000 years.

Results of this study will allow assessment of the hypothesis that ice streams played a significant role in the most recent disintegration of the WAIS by testing the validity of various ice sheet reconstructions. Additionally, better characterization of the configuration of the Ross Ice Sheet during the last glacial maximum will improve the quality and reliability of models of the past and future characteristics of Antarctic ice sheet behavior.

ABSTRACT
OPP-0004233
Andrews

The late Quaternary extent and thickness of ice and the deglacial chronology of the Northwest Peninsula of Iceland are poorly constrained. The Principal Investigators will conduct a collaborative research project on the glacial and deglacial history of the western coastline and uplands of western Hunafloi, NW Iceland, and the adjacent marine trough, Hunafloaall. The proposal builds on marine cruises in 1996, 1997 and 1999, and on a pilot field program conducted in the summer of 2000. The purpose of the project is to resolve the late Quaternary glacial history of part of NW Iceland and to correlate the terrestrial record with the marine record. This research will add new insight into the glacial history of marine arctic margins and a very old debate on biological "refugia."
At least two models for the reconstruction of glacial extent during the Lower Glacial Maximum (LGM) and subsequent retreat have been suggested for Iceland, but these are based on only limited radiocarbon dates. In the NW Peninsula, the glacial reconstructions vary from an extensive ice cover model with no ice free areas to a refugia model in which ice free areas existed on the high plateaus with vascular plants surviving glaciation. These studies are based entirely on terrestrial glacial evidence and interpretations, but this must be intimately linked to the offshore sedimentary record of glacial and marine sediments. High-resolution 3.5 kHz acoustic stratigraphy and marine cores from the Hunafloaall trough suggest that the LGM extent may have been relatively restricted. In Hunafloaall, a basal dimicton containing foraminifera, is overlain by a thin (<2 m) sequence of IRD-rich glacial-marine and marine sediments. Basal dates on the IRD-rich muds indicate deglaciation occurred by 13 thousand years ago (ka). Dates from the dimictons are finite and > 20 ka. Such a thin deglacial sequence provides a major contrast with SW Iceland where the deglacial sediments reach thickness of 10-40+ m. The virtual absence of deglacial sediments in Hunafloaall is perplexing and raises serious questions of ice extent and chronology on the adjacent NW Peninsula.
Cosmogenic isotope exposure dating techniques will be used to constrain "maximum" and "minimum" models of glacial extent. Specifically, 3He and 36CI isotopes will be used to date the basaltic upland surfaces, end and lateral moraines, and glacial erratics. Tephrachronology and physical properties of the sediment samples will be used to link the terrestrial and marine records.
The Principal Investigators will continue their field and laboratory investigations on: 1) the vertical and lateral extent of glaciation along this coastline, including collection of samples for cosmogenic isotope exposure dating; 2) the pattern and timing of deglaciation and any subsequent glacier expansion; 3) investigation of the marine cores with the view toward discriminating between tills and glacial marine dimictons, and with a focus on more accurately dating the onset of deglaciation; and 4) changes in relative sea level as a measure of ice load and history. The field work will continue and expand a pilot program that began in summer of 2000, involving the Universities of Colorado, Iceland, Goteborg, and Edinburgh.

The Principal Investigator is requesting funds requested to continue Office of Polar Programs (OPP) support for graduate student participation in the annual Arctic Workshops. Over the last eight years, OPP has supported attendance at this workshop through payments of registration, per diem meals, and lodging for four nights. The last grant supported the Arctic Workshop at the Universities of Ottawa, Colorado, Washington, and Massachusetts. The budget is based on an attendance of 25 students, but the actual number per workshop was closer to 50. The next three workshops will be held at the University of Colorado, the University of Tromso (Norway), and the University of Colorado. The composition of the Arctic Workshops typically consists of about 55% professional Arctic scientists (academic and government), and 45% graduate students. A major effort is placed toward providing all the graduates with a forum for their research and to establish the appropriate "network" with their peers. The Arctic Workshops have participants from several countries with significant attendance from the United States, Canada, Norway, Iceland, Sweden, Germany/Austria, and the United Kingdom.

This award will enable researchers to use a multi-proxy approach to evaluate environmental variability from sites capturing the dynamics between the Arctic and Atlantic environment. The goal of the research is to determine the range, trends, and nature of climate variability in the region during the Holocene. The broad geographic extent of the research strategy is designed to allow evaluation of the influences and complexities of different components of the climate system.

Holocene paleoclimate records of centennial temporal resolution will be produced from four long sediment cores recovered in 1999 in contrasting hydrographic settings. The sites include cores from the Labrador Shelf, the Southwest Iceland margin, the North Iceland shelf, and the East Greenland shelf. The sites were exposed to ice-sheet/ocean interactions during the final deglaciation phases of the Laurentide, Greenland, and Iceland ice sheets.

Such research would help provide an improved understanding of the dramatic environmental changes being observed in the Arctic today (i.e., marked retreat and thinning of the sea-ice cover and melting and thinning of the Greenland Ice Sheet, increased discharge of the Russian rivers). Whether these current changes are within the range of natural variability, or are unprecedented, can be evaluated by the data preserved in sediment cores and comparing them to a spectrum of cryosphere-ocean interactions in the northern North Atlantic.

In summary, this research on high latitude continental margins opens a promising new archive of past climatic variability. The research has broader implications in areas of education and international research co-operation as it will provide a graduate student with a unique opportunity to actively pursue magnesium/calcium temperature calibrations for water temperatures less than 10degrees-Celsius. Successful development of this proxy would be a significant contribution to the field of paleoclimatology.

ABSTRACT
Andrews
OPP-0327187

A better understanding of future environmental change is a pressing need of human society today and projections can be tested and evaluated by reconstructing the ranges and rates of past changes. The goal of this project is to develop a quantitative reconstruction of the marine climate Vestfirdir, north Iceland over the last 2000 years. Northern Iceland was chosen because of its sensitive location. This small area encapsulates climatic changes throughout much of the North Atlantic because it lies at the boundary between the Atlantic and Polar/Arctic realms, which drive much of the change. In addition, this is ideal area for climate reconstruction because it has 1) an extensive database of modern instrumental climate data, 2) a 1,200 year historical documentary climate record, and 3) well dated, high-resolution sediment cores containing an archive of natural climate variability. The research will reconstruct seasonal and annual temperature variations based on the stable isotopic composition of marine molluscs from three marine cores in Vestfirdir. The isotope data will be calibrated against the modern instrumental record and applied to molluscs in the cores. Seasonal to annual temperature estimates will be achieved through analysis of 60 individuals, with life spans of two to ten years, that lived during modern times, through the Settlement of Iceland (AD 871) and beyond the interval of human impact to c. 2000 years ago. The use of the micromilled molluscs in marine cores is the only way, at present to obtain seasonally- to-annually resolved climate data from Iceland, beyond the instrumental and documentary record. The short, but annually resolved records are placed within an environmental framework through analysis of other traditional proxy records. Drawing on earlier analyses of these cores, major environmental changes of the past are identified. These include a prolonged "cold" interval between 70 and 400 yr B.P. (ca. AD 1930 back to 1600), an interval with lower ?18O (CaCO3) (warmer) values around AD 1000, and a cool interval centered at AD 670. The project will select molluscs for analysis within these .warm. and .cold. intervals. In order to study the human dimensions of these changes, emphasis will be placed on the period from the Settlement of Iceland (c. AD 871) to the present. Isotope-based temperature reconstructions will be used to evaluate historical records of Icelandic sea-ice incidence and fisheries catches, with the main goals of: 1) determining the role of oceanic variability in the productivity of Icelandic fisheries; and 2) isolating periods when non-climatic factors might have played a role in fisheries variations. The impact of the reconstructed marine climates on biodiversity will be measured by changes in benthic foraminiferal assemblages.

Broader Impacts
This project represents a multidisciplinary evaluation and analysis of the role of climate change on the nearshore marine climate and its association with changes in historical fisheries practices and catches. It represents an international effort, with researchers from the USA and Canada and with co-operation from several colleagues in Iceland. It also fosters collaboration between NSF and Rannis (the Icelandic Science Foundation). Links with the archeological community currently working on the zooarcheology of sites in northern Iceland will be strengthened. This collaboration will enable analysis of stable isotopes on fish otoliths found in the refuse from these sites and comparison of these variations with the stable isotope data from the marine cores. The project will educate both graduate and undergraduate students, and will be beneficial in the training of young scientists in geochemical methods and micro- and macro -paleontology.

EAR-0447129
Anderson

This grant provides partial support for an dual system ion chromatograph (IC) equipped with automated sampling system for determination of major anions and cations in aqueous solution. The IC will be used for investigations of surficial hydrochemcial processes in support of paleoclimate, paleoceanographic and alpine research. The IC will facilitate ongoing and future research and research training by University of Colorado faculty, research scientists and their students involved with the Institute for Arctic and Alpine Research (INSTAAR) which draws on faculty and students across multiple UC departments.
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This award uses funds to collect and analyze data on quartz and dolomite mineral concentrations and fluxes in a series of sites around Iceland, east Greenland, and the Labrador shelf, with the goal of examining the Holocene spatial and temporal variability of these specific mineral species as measures of drift ice presence or absence and severity.

Variations in the extent and duration of drift ice (i.e., icebergs plus various forms of sea ice) in the marginal Seas of the North Atlantic (the Greenland and Iceland Seas, and Baffin Bay/Labrador Sea) influence the climate of adjacent land areas and whose effects can be propagated downstream by both atmospheric and ocean circulation.

Reconstructions of variations in the delivery of IRD (ice-rafted debris) to sites in the North Atlantic (based on counts of hematite-stained quartz sand grains) show an overall decrease in IRD from 12,000 years ago to the present, with a series of oscillations spaced at ~1,500 year intervals. In contrast, the IRD on the glacial fraction from sites on the east Greenland shelf show a mid-Holocene interval of little IRD followed by a strong increase during the last 5,000-6,000 years.

Initial results suggest that the generally accepted paradigm that Holocene IRD in the North Atlantic region is captured in hematite-stained quartz variations, dominated by a 1,500-yr periodicity, is not correct and that mechanisms other than drift ice are required to explain the pervasive signal.

The research will help solve a puzzle of sorts as to why marine sites in the North Atlantic differ in their signal of sedimentological response to climate variability. The research strategy posses strong international collaborations between scientists in the United States, Canada, Norway, and Germany.

Intellectual Merit: The Principal Investigators will reconstruct the Late Quaternary-Holocene behavior of Jakobshavns Isbrae (JAKIB) in western Greenland, one of the largest ice streams draining the modern Greenland Ice Sheet (GIS). The period from the Last Glacial Maximum (LGM) to the present will be studied because it involves the most recent large scale change in the mass-balance of the ice sheet, it is the period that will be best preserved in continental shelf sediments, and it is the period for which the highest resolution proxy records of paleo-climate from the Greenland ice cores are available. Given the scale of this ice stream and the size of its associated drainage basin, the investigation will provide information on the Late-Quaternary-Holocene behavior and stability of a major area of the GIS. This research will allow assessment of the links between deglaciation and internal and external environmental controls, such as the influence of inflowing Atlantic Water, and will facilitate modeling of the likely future behavior of the GIS. The Principal Investigators will participate in a research cruise of the British Research Vessel, Sir James Clark Ross, to West Greenland in the late summer of 2007 and collaborate with British colleagues on the post-cruise, interdisciplinary program of laboratory work and modeling. Well-dated, high-resolution sediment records from a transect of sites extending from the shelf edge and along the shelf trough, to sites within Disko Bugt both proximal and distal to the modern ice margin will be acquired on the basis of geophysical data. The hypotheses to test using these cores are:
Hypothesis 1: Glacier ice extent and interactions between the West Greenland Current
and the GIS are recorded in the foraminiferal faunas, mineralogical variations, and Sm and Nd isotopic compositions of the sediments.
Hypothesis 2: The West Greenland Current has changed in strength, flowpath and
watermass composition from the LGM through the Holocene. These variations have
played and continue to play a key role in ice-sheet behavior.

Broader Impacts: The underlying rationale for this research is to determine if recent
(last ~ 100 yr) observed changes to the mass balance of the GIS reflect natural variability
in ice sheet dynamics, or if they relate to anthropogenically-induced climate warming.
Key to resolving this is an understanding of ice sheet behavior since the LGM and
including periods in the past near Greenland that were as warm or, even warmer than
today, such as the middle Holocene optimum. This research will make new discoveries
concerning the timing and extent of the Greenland Ice Sheet at the LGM on its western
margin, and the behavior of the JAKIB ice stream during deglaciation, new information
that will inform paleoceanographers and climate and sea-level modelers. This project is an international effort. It will support a U.S. PhD student, and two undergraduate students. It will involve international student exchanges between the University of Colorado and the United Kingdom. The data acquired will be lodged in the NOAA Paleoclimate Database.

This project integrates modeling and paleoenvironmental data to obtain a better understanding of the role of volcanism in the Arctic System, and to better utilize widespread tephra layers to date and synchronize paleoenvironmental records across the Arctic.

The Arctic includes major centers of volcanism in the North Atlantic and the North Pacific sectors. Stratospheric aerosols derived from either Arctic or tropical volcanism alter the radiative balance of the Arctic, which in turn influences atmospheric circulation with global consequences. Reduced summer insolation can lead to substantial Arctic cooling of a few years' duration, but these perturbations may produce longer impacts if the system passes through a threshold condition, whereby strong positive feedbacks yield changes in the state of the Arctic System. New paleodata suggest that dramatic increases in terrestrial ice caps in Arctic Canada lasting several centuries occurred following two of the largest eruptions of the past millennium, during the transition into the Little Ice Age. Explosive Arctic volcanism can produce large volumes of source- and time-diagnostic tephra, with extensive distributions. These tephra layers provide time-synchronous marker horizons that constrain the geochronology of paleoenvironmental records and serve to precisely synchronize records derived from lacustrine, marine, and ice-sheet archives, thereby allowing a better assessment of leads and lags in the climate system.

An international research team has been assembled to assess the impact of both Arctic and tropical eruptions on the Arctic System through climate modeling and to optimize the utility of tephras in paleoenvironmental studies throughout the North Atlantic Arctic. This represents the US contribution. Specific objectives of this effort include:
- Establish a standardized geochemical inventory of Icelandic marker tephra erupted over the past 12,000 years, and develop criteria to differentiate Icelandic from North Pacific tephra.
- Improve techniques to identify and extract microtephra from sedimentary archives.
- Extend proximal-derived Icelandic tephra geochemical fingerprinting to microtephra in distal lacustrine, marine and Greenland ice-core archives.
- Develop generalized maps of plume trajectories for most major Icelandic eruptions.
- Evaluate the sensitivity of the Arctic System to high- and low-latitude eruptions through climate modeling and comparisons of model output to paleoenvironmental reconstructions.

This award will provide funds to test three hypotheses related to the formation of intermediate and deep water in the Nordic Seas north of Iceland. Specifically, was 1) Denmark Straight Overflow Water (DSOW) formation dampened by freshening of Atlantic Water entering the Nordic Seas through the end of the deglaciation of the Laurentide Ice Sheet, ca. 6,700 cal years ago? 2) Does the middle Holocene interval of greatest DSOW flow correspond to a time of minimal freshwater forcing from north and south and maximal salinity and inflow of the Irminger Current? 3) Was diminished DSOW formation in the late Holocene due to freshwater forcing from the Arctic Ocean by southward advancing Polar Water and sea ice? These hypotheses will be tested via analyses of sediment geochemistry and Mg/Ca, d18O and Cd/Ca of foraminifera assemblages from a suite of North Atlantic deep sea cores, as part of a broader international collaboration including the IPY project WARMPAST. Broader impacts include graduate and undergraduate involvement in the research, a strong international collaborative component and research on a societally-relevant scientific question related to ocean-climate linkages and mechanisms of climate change during the Holocene (last 10,000 years).

Historical observations and theory suggest the importance of the extent and duration of
drift ice on the Climate System through changes in the Hemispheric albedo and the impact of freshwater export from the Arctic Ocean and Greenland Ice Sheet on the Thermohaline Circulation. Funds are provided to develop 50-100 yr resolution records of changes in sea ice export from the Arctic Ocean and iceberg transport from tidewater ice streams of NE Greenland that reach the Denmark Strait and to develop a detailed history of ice-rafted debris (IRD) over the last 12,000 cal yr BP. Denmark Strait is believed to be a critical area for study as it lies at the boundary between the southward export of Polar and Arctic waters and the northwestern limb of the North Atlantic Drift in the form of the Irminger Current. The research will explore a sources-to-sink model along the ENE/E Greenland shelf and across the Denmark Strait using sediment characteristics to document spatial and temporal changes in composition in a series of well-dated, high-resolution cores from either side of the Denmark Strait and along the NE Greenland shelf. This information will be used to infer changes in the transport of sea ice through the Denmark Strait.

Given the ongoing observations of changing sea ice character in the Arctic, changes in the flux of sea ice into the Greenland-Norwegian Seas and the North Atlantic Ocean, and possible acceleration of ice loss from the Greenland Ice Sheet through iceberg calving, a better understanding of how these processes varied in the past will help inform projections of future climate variations. This project will develop data sets that contribute to that understanding.

The proposed research will evaluate how ocean warming contributed to past ice sheet dynamics through study of the Last Glacial Maximum (LGM) through early Holocene behavior of ice streams draining into Baffin Bay. This research will provide a new context for understanding ice sheet response to past warm periods, in particular, the Bølling/Allerod interstadial period, which hosted rapid sea level rise and abrupt climate warming after the LGM. At the LGM the Greenland Ice Sheet (GIS) was one of three large ice sheets terminating via large, fast flowing ice streams into Baffin Bay. This project will
study the past history, dynamics, and ice-sheet ocean interactions in Baffin Bay, and the role of ocean warming in ice sheet demise, via multi-proxy analysis of existing (2008 and 2009) sediment cores from the West Greenland continental slope. Data from this proposal will be used to model freshwater flux from the ice streams, and will provide new information on what role the Greenland Ice Sheet played in past sea-level rise as the LGM ice sheet began to shed as much as 4.6 m of sea level equivalent. The research will test three hypotheses using foraminiferal faunas, sediment mineralogy, stable isotope analyses, stratigraphy of iceberg rafted detritus (IRD), and visible diffuse spectral reflectance data:
1. The western margin of the GIS advanced during stadials and retreated during interstadials in
response to the presence or absence of ocean warming via the West Greenland Current.
2. Peaks of ice-berg rafted material (IRD) result from two distinct processes: Proximal IRD is
derived from retreat of the GIS off the shelf edge, whereas distal IRD results from collapse of the
Laurentide Ice Sheet and Innutian Ice Sheet/NW Greenland margins in northern Baffin Bay.
3. Advection of warm water along the West Greenland margin causes enhanced melting of
northern Baffin Bay icebergs and sea ice at the polar front, forming an IRD belt along the W.
Greenland margin, which preserves a record of ice sheet-discharge events under conditions of
ocean warming.

The GIS is losing mass in response to modern warming. It stores enough fresh water to raise global sea level by 6.5 m, making its sensitivity to warming a major societal concern. It is anticipated that the sensitivity and response of the GIS to past warming, which are the foci of this project, will help constrain projections of the future evolution of the GIS.

This project will take a multi-disciplinary approach to understanding the response of Petermann Glacier in northern Greenland to climate change in the past. Petermann Glacier drains a significant fraction of the northern Greenland ice sheet and terminates in a large floating ice shelf that is sensitive to ice-ocean interactions. Ice retreat over the last decade opens access to the fjord and presents an opportunity to understand sedimentation processes under the area previously covered by ice shelf and to calibrate reconstructions of past ice shelf variations. Using a variety of technologies and approaches on land, ice, and at sea, the investigators will map the bottom of the fjord in front of and under the ice shelf; reconstruct ocean conditions and their role in ice shelf variations through time; reconstruct the past extent of the glacier on land and the floating ice shelf; and reconstruct local relative sea level. Together these efforts will create a comprehensive picture of the climate conditions and response of the Petermann Glacier to these conditions over the last 10,000 years.

Of key interest will be the timing, extent, rates of change, and variability (on land and in the sea) during the early Holocene when local relative sea level was over 100 meters higher than today (due to lagging isostatic rebound of the crust in response to deglaciation), but the inland ice sheet was still large relative to today. The investigators will address dynamic responses to multiple interacting variables over a range of response times (from tens to thousands of years) relevant to potential future impacts. Specific research questions include: 1) How sensitive is Petermann ice shelf extent to documented climate changes within the Holocene? 2) Is shelf response independent of, or linked to, variations in the grounded Petermann Glacier, ocean thermal conditions, or relative sea level (i.e., sill depth)? 3) What are the rates of change and variability of these systems in response to early Holocene warming, Neoglacial cooling, and recent warming? The project will support several young investigators and will provide them with both ship and land-based training experiences. The project includes significant international collaborations, with substantial in-kind contributions from non-U.S. sources that add value to the project. Planned outreach includes teacher participation in the field program and meaningful classroom involvement at several levels.

Changes in the amount of sea ice and low salinity surface water (together called freshwater) that flow from the Arctic Ocean to the North Atlantic have global ocean circulation and climate impacts. The research involves analysis of the timing and consequences of the opening of the western route for Arctic freshwater flux after the retreat of glacier ice at the end of the last glaciation. The Arctic freshwater flows through the western route to the Labrador Sea, which is a critical area of deep ocean convection. Diverse analyses of sediment cores from northern Baffin Bay and computer modeling will be used to document and explore the large changes in sea-ice cover, Arctic freshwater flux, ocean circulation, marine productivity, and ocean acidification over the last 11,000 years that are associated with opening of the western freshwater route. An important component of the research is to study the history of the North Water Polynya (NOW), an oasis of high productivity and low sea-ice cover that forms where the Arctic freshwater enters northern Baffin Bay. The productivity of the NOW owes to the high nutrient content of the Arctic freshwater and to the blockage of Arctic sea-ice floes by the constricted channels forming the gateway. The NOW is a hotspot of biological productivity that has attracted humans to the area for millennia and sustains Arctic communities today. Both the history of freshwater flux via the western freshwater route and the history of the NOW are very poorly known, yet the behavior of this system is poised to change in response to continuing reductions in Arctic sea-ice cover. The understanding of how the opening of the western route of Arctic freshwater and the initiation of the NOW have changed through time will provide context to understand how these systems will affect the Arctic systems and global climate in future.

The project uses existing sediment cores from the NOW polynya, and areas upstream of and downstream from it using both novel (nutrient tracers from Inductively Coupled Plasma Mass Spectrometry and algal biomarkers) and traditional (quantitative X-ray mineralogy, foraminiferal assemblages, stable C and O isotopes) proxies, climate modeling with the Community Earth System Model (CESM) and Glacial Isostatic Adjustment modeling and chronology development (radiocarbon and paleomagnetic secular variation) to test three hypotheses: Hypothesis 1: The opening of the western freshwater route of the Arctic-Atlantic throughflow changed the freshwater outflow to the North Atlantic with consequences for the Atlantic Meridional Overturning Circulation (AMOC). Hypothesis 2: Significant shallowing of the CAA channels by glacial isostatic uplift has changed the composition of the Arctic outflow with consequences for carbonate preservation and the AMOC. Hypothesis 3: The NOW formed in the middle to late Holocene as a consequence of increased Arctic sea-ice. The project is an international effort involving Canadian and EU cooperation and foreign graduate student interaction with CU faculty and scientists. It will provide support and mentoring for a female post-doc who will receive training in novel biogeochemical laboratory techniques. A PhD student will work on the CESM modeling. Several undergraduate students will receive training and participate in the research.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.