John J. Cassano - US grants

The objectives of this research are to detect and document changes in the storage of freshwater in the Arctic regions of the Western Canadian, Alaskan, and Eastern Siberian Arctic, to ascribe those changes to their land cover or climate source, and assess the impacts of past and future variations in storage components (e.g., active layer depth, lake volume) on freshwater inputs into the Arctic Ocean. The aim is to characterize the changing hydrologic regime spatially to facilitate accurate projections of future hydrologic conditions and to develop a numerical modeling capability that 1) accurately captures contemporary climatic and hydrologic dynamics, 2) projects reasonably accurate responses to future scenarios and 3) incorporates well documented algorithms that will be distributed to other modeling groups wishing to include dynamic land surface processes in arctic regions (e.g., for studies of vegetation dynamics or gas flux). The investigators will also provide a pan-Arctic perspective by using spatially-based model results to develop a statistically-based model.
The research is divided broadly into two main components: process-level hydrologic studies and large-scale atmospheric studies, with a well-defined approach to bridge the scale differences. Process-level studies include field observations and analyses of the storage components in the hydrological cycle as well as modeling of their role in the hydrological cycle. Field studies include surveys of the main storage components, with literature searches and remote sensing filling in many of the gaps. Field studies on the watershed scale will also be conducted at several small watersheds along North/South transects covering the Middle Yukon, Kuparuk, Upper Yukon, Mackenzie and Lena watersheds where long-term records and on-going measurement programs exist. The WaterWERCs model will be applied to these small sub-watersheds for calibration and validation using contemporary records, and to the entire watersheds for both climate scenarios of the past, present and future driven from our atmospheric modeling. The atmospheric model, PAM, is a state-of-the-art regional climate model that will be tailored for use in a pan-Arctic setting and will be driven by gridded atmospheric re-analyses. The atmospheric model results will be validated with available observational data and the gridded model output will be used to force a hydrologic model.

This award will provide funds to deploy an array of seven automatic weather stations (AWS) in the region to the east and south of Ross Island, Antarctica, in order to characterize the surface environment surrounding the major air flow corridors on the Ross Ice Shelf. These air streams have been identified as the primary corridor for the transport of mass, heat, and momentum between Antarctica and subpolar latitudes. An understanding of the basic physical characteristics of these air streams and their modulation by the frequent cyclonic activity in the Ross Sea to the north is necessary to advance our capabilities in forecasting weather in the Ross Island and McMurdo area. Previous work has established the Ross Sea region as critically important in the connection of Antarctic processes to the rest of the globe on a variety of time scales.
This two-year study will include AWS deployment, analysis of existing data sets and the initiation of model simulations, and will form one of the bases of a planned Ross Island Meteorological Experiment.

The climate of the Arctic is changing. According to the Arctic Climate Impact Assessment (ACIA), "Arctic climate is now warming rapidly, and much larger changes are projected". These changes are of concern because of their possible implications for global ocean circulation. The ARCSS Freshwater Integration Study (FWI) was designed to address the scientific basis of many of these broader issues that are related to the arctic freshwater cycle, especially over land. In particular, FWI has the objective of addressing "... key, unresolved issues ... [that are] fundamentally cross-disciplinary and synthetic in nature". Three of these issues deal directly with the coupled implications of arctic climate and the water and energy balances of the region. NSF funded a group of 18 FWI projects in 2002, which together with subsequent ARCSS projects were intended to address the FWI questions outlined above. However there is a need for synthesis activities to exploit more fully results of the FWI projects. This work will utilize research results from the FWI projects that have a substantial land surface activity, and will incorporate the results in a synthesis activity that will document and attribute observed change in the arctic hydrologic cycle, both for the climate of the region, and the global climate system. The primary synthesis mechanism will be a coupled regional land-atmosphere model (either polar WRF or MM5), and (more limited use) of a global model of medium complexity of the ocean-land-atmosphere system. The overarching science question to be addressed is: How do changes in arctic land processes affect the climate of the region, what are the implications of these changes for the arctic hydrologic cycle (including coupling and feedbacks with the atmosphere), and what are the impacts of changes in the arctic freshwater system on global climate?

The research will address two supporting science questions: 1) How can the results from the FWI studies be used to better understand the hydrologic processes affecting observed change in the freshwater balance of the pan arctic land system? and 2) To what extent are the observed changes in Arctic terrestrial hydrologic cycle due to imported change from other regions (via atmospheric processes), and to what extent are the observed terrestrial hydrologic changes exported to the atmosphere and to the global ocean system? The first question leads to attribution questions regarding which hydrologic processes have contributed to observed change, and will be addressed using a strategy of uncoupled, partially coupled, and fully coupled land-atmosphere modeling at the pan-arctic scale. Addressing the second question will require documenting the effect of hydrologic change on global climate (via changes in the oceans). It will be addressed through use of a coupled GLOBAL land-ocean-atmosphere model of medium complexity (University of Victoria ESCM climate model).

To date our understanding of change in the Arctic region and its broader role in global climate has been limited. This research seeks to provide a comprehensive view of key hydrological processes within the Arctic system and how they interact regionally and with the global system via oceanic and atmospheric pathways. It is expected that this will result in a better understanding of how hydrologic processes have contributed to observed change and the contribution from extra-Arctic processes. Detailed analysis of these interactions and feedbacks will provide valuable information to the climate community for understanding the role of the Arctic in climate variability and change.

This is a three-year project to maintain and augment as necessary, the network of approximately fifty automatic weather stations established on the antarctic continent and on several surrounding islands. These weather stations measure surface wind, pressure, temperature, humidity, and in some instances other atmospheric variables, such as snow accumulation and incident solar radiation, and report these via satellite to a number of ground stations. The data are used for operational weather forecasting in support of the United States Antarctic program, for global forecasting through the WMO Global Telecommunications System, for climatological records, and for research purposes. The AWS network, which began as a small-scale program in 1980, has been extremely reliable and has proven indispensable for both forecasting and research purposes.

This effort will test the hypothesis that the loss of arctic sea ice and northern high latitude snow cover will invoke changes in the seasonality, spatial distribution and magnitudes of precipitation (P) and net precipitation (P-E) over the Arctic, which along with attendant changes in temperature, have ramifications for the freshwater budget of the Arctic Ocean and the mass balance of the Greenland ice sheet.

The researchers expect that: (a) sea ice loss will lead to an increase in available water vapor over the Arctic Ocean and peripheral seas, most pronounced in autumn and winter, when delayed ice formation and thinner ice will promote large vertical fluxes of heat and moisture into the atmosphere; (b) loss of sea ice and terrestrial snow cover will invoke changes in arctic circulation patterns and hence patterns of water vapor convergence, driven in autumn and winter by enhanced vertical heat fluxes and during the warm season by altered differential heating over the Arctic Ocean and surrounding land; (c) in lying "downwind" of the Arctic Ocean as well as adjacent to the (presently) partially ice-covered East Greenland Sea and Baffin Bay, the Greenland ice sheet will feel these changes both through impacts on accumulation and surface melt.

The analysis tool will be Polar WRF, a recently developed regional climate model optimized for polar applications. Control simulations will be conducted for several arctic domains, focusing on recent years which are characterized by extremely low September sea ice extent, with lateral forcing supplied from the NCEP/NCAR reanalysis, and sea ice conditions prescribed from satellite-based observations. Generated fields of key hydrologic variables (precipitable water, precipitation, vapor flux convergence, net precipitation, temperature) and atmospheric circulation will be contrasted with those from a series of experiments with altered sea ice and snow cover. These will include simulations with climatological maximum winter ice extent and concentration through the annual cycle, prescribed reductions in ice extent and concentration larger than those observed, 100% and 0% terrestrial snow cover maintained over the annual cycle but with observed sea ice conditions, and observed sea ice conditions but with increased sea surface temperature over open water areas in summer.

Antarctic polynyas are the ice free zones often persisting in continental sea ice. Characterization of the lower atmosphere properties, air-sea surface heat fluxes and corresponding ocean depth profiles of Antarctic polynyas, especially during strong wind events, is needed for a more detailed understanding of the role of polynya in the production of latent-heat type sea ice and the formation, through brine rejection, of dense ocean bottom waters.

Broader impacts: A key technological innovation, the use of instrumented uninhabited aircraft systems (UAS), will be employed to enable the persistent and safe observation of the interaction of light and strong katabatic wind fields with the Terra Nova Bay (Victoria Land, Antarctica) polynya waters during late winter and early summer time frames. The use of UAS observational platforms on the continent to date has to date been modest, but demonstration of their versatility and effectiveness in surveying and observing mode is a welcome development. The projects use of UAS platforms by University of Colorado and LDEO (Columbia) researchers is both high risk, and potentially transformative for the systematic data measurement tasks that many Antarctic science applications increasingly require.

This is a collaborative project involving four institutions. The proposed research addresses two major questions related to climate in the eastern Alaskan Arctic: 1) How has climate, terrestrial ecology, and pollutant transport changed over the past 250 years in this region, based on ice core reconstructions from McCall Glacier? and 2) How well can we overcome the challenges of core proxy interpretations from ice cores taken from small polythermal valley glaciers through modern-process studies? To answer these questions the investigators conduct an inter-disciplinary analysis of ice core proxies, atmospheric dynamics, modern processes, and numerical ice flow modeling. A 152-meter long core has already been drilled through McCall Glacier and analyzed for 35 chemical proxies. The proposed work will focus on 1) interpretation of these proxies, 2) analysis of pollen in the core, 3) process studies to identify sources of pollen to McCall Glacier, 4) tying the weather and climate record of the past 50 years to the upper section of the core, 5) continuing 3D flow modeling of the glacier and local weather observations, 6) conducting modern process investigations of the effects of seasonal melt on the generation of the core proxy record. The project will support two graduate students.

The Antarctic Automatic Weather Station (AWS) network, first commenced in 1978, is the most extensive meteorological observing system on the Antarctic continent, approaching its 30th year at many of its key sites. Its prime focus as a long term observational record is vital to the measurement of the near surface climatology of the Antarctic atmosphere. AWS units measure air-temperature, pressure, wind speed and direction at a nominal surface height of 3m. Other parameters such as relative humidity and snow accumulation may also be taken. Observational data from the AWS are collected via the DCS Argos system aboard either NOAA or MetOp polar orbiting satellites and thus made available globally, in near real time via the GTS (Global Telecommunications System), to operational and synoptic weather forecasters. The surface observations from the AWS network also are often used to check on satellite and remote sensing observations, and the simulations of Global Climate Models (GCMs). Research instances of its use in this project include continued development of the climatology of the Antarctic atmosphere and surface wind studies of the Ross Ice Shelf.

The AWS observations benefit the broader earth system science community, supporting research activities ranging from paleoclimate studies to penguin phenology.

Changes in temperature and precipitation extremes could be especially large in the Arctic, which is projected to have some of the greatest anthropogenic warming. Consistency of physical causes of extreme temperature and precipitation in observations and in simulations of past and future scenarios can indicate the robustness of projected changes. Consistent simulations of extremes by several models can provide much greater sampling of extreme events, leading to more confident assessment of the changing risk of extreme events. The PI's will investigate possible changes in extreme temperature and precipitation events in the Arctic using observational records and output from the CORDEX (regional) and CMIP5 (global) climate modeling programs. The project aims to detect, attribute, and understand changes in extreme temperature or precipitation through an analytical framework that focuses on both the extreme temperature or precipitation events and the physical processes which support them. The PI's will assess observed and simulated changes in extreme precipitation processes using a pattern-recognition tool, Self-Organizing Maps (SOMs), that allows construction of a coherent, multivariate view of collections of extreme events. The methods developed will also have application to studies of extremes in other regions of the planet, extending capacity for assessing changes in extremes and their underlying physical causes. The project will train a new generation of scientists equipped to perform ensemble analysis of the changes in extremes and the uncertainties in their projection.

Antarctic coastal polynas are, at the same time, sea-ice free sites and 'sea-ice factories'. They are open water surface locations where water mass transformation and densification occurs, and where atmospheric exchanges with the deep ocean circulation are established. Various models of the formation and persistence of these productive and diverse ocean ecosystems are hampered by the relative lack of in situ meteorological and physical oceanographic observations, especially during the inhospitable conditions of their formation and activity during the polar night.


Characterization of the lower atmosphere properties, air-sea surface heat fluxes and corresponding ocean hydrographic profiles of Antarctic polynyas, especially during strong wind events, is sought for a more detailed understanding of the role of polynyas in the production of latent-heat type sea ice and the formation, through sea ice brine rejection, of dense ocean bottom waters

A key technological innovation in this work continues to be the use of instrumented unmanned aircraft systems (UAS), to enable the persistent and safe observation of the interaction of light and strong katabatic wind fields, and mesocale cyclones in the Terra Nova Bay (Victoria Land, Antarctica) polynya waters during late winter and early summer time frames.

The overarching goal of the project is to advance understanding of Arctic climate system operation and variability to improve model prediction of Arctic climate change at decadal to centennial scales. A set of specific objectives is proposed centered on the following main science hypothesis:
Given the projections of continued global warming and its northern high-latitude amplification, the Arctic will become nearly ice-free during summer in the near future, resulting in altered physical state of and interconnections within the Arctic climate system.
To confirm or disprove the above hypothesis, our approach is to use subsets of model components and fully coupled RACM to address the following specific objectives:
- Identify potential improvements in the simulated sea ice thickness distribution and deformation due to increasing model resolution and representation of fine-scale ice-ocean interactions
- Investigate effects of shrinking and thinning sea ice on ice kinematics and its consequences on changing air-ice and ice-ocean interactions
- Examine and quantify consequences of melting sea ice on the increased upper ocean heat content and its potential for increased ice melt due to a positive ice-ocean feedback loop
- Assess the influence of excess oceanic heat release, especially in fall and winter, on potentially enhancing cyclonic tendency in the atmosphere
- Explore the importance of increased sea ice melt and runoff to the Arctic hydrological cycle and its acceleration in the context of first-year ice growth and survival
- Integrate positive and negative feedback processes into model simulations of warming climate scenario to determine their net impact on the long-term state of Arctic ice cover
- Identify physical and numerical requirements of future GCMs to significantly improve model skill in representing past and present and in predicting future Arctic climate change.
A hierarchy of well designed one-way and fully coupled regional climate system model experiments will focus on the above objectives. Such experiments will provide advanced insight into the behavior of the Arctic climate system that is not currently attainable using either individual regional component models or GCMs. The proposed project helps to lay the foundation for a community regional Arctic System Model as recommended in the recently published report to NSF. This research will also address or facilitate other studies related to potential implications of Arctic sea ice melt and warming climate, including consequences for the global ocean thermohaline circulation, Greenland ice sheet, ecosystem, shipping, natural resource development, policymaking and defense. Output from the baseline simulations will be made available to the community through either the ARCSS Data Coordination Center or a Live Access Server at the Naval Postgraduate School, to be developed in support of this project.

The Antarctic Automatic Weather Station (AAWS) network, first commenced in 1978, is the most extensive ground meteorological network in the Antarctic, approaching its 30th year at several of its installations. Its prime focus as a long term observational record is to measure the near surface weather and climatology of the Antarctic atmosphere. AWS sites measure air-temperature, pressure, wind speed and direction at a nominal surface height of 3m. Other parameters such as relative humidity and snow accumulation may also be measured. Observational data from the AWS are collected via the DCS Argos system aboard either NOAA or MetOp polar orbiting satellites and thus made available in near real time to operational and synoptic weather forecasters.

The surface observations from the AAWS network are important records for recent climate change and meteorological processes. The surface observations from the AAWS network are also used operationally, and in the planning of field work. The surface observations from the AAWS network have been used to check on satellite and remote sensing observations.

Nontechnical

This project will explore the characteristics, variability and environmental impacts of a little-studied arctic seasonal atmospheric feature called the Summer Arctic Frontal Zone (AFZ), and how it may change over the next century. Little is known about variability in the AFZ or how it will change in the future. The feature is overlain by a high level jet-like feature, and areas where the AFZ are most pronounced are regions of frequent storm genesis, so understanding it is important to understand and predict weather events. In linking the arctic atmosphere, ocean, land surface and the hydrologic cycle, this study of the AFZ adopts a systems perspective, and steeping the next generation of researchers in systems studies is important for maintaining U.S. preeminence in environmental science, so the project is strongly geared towards support of a graduate student. Results from this study will be integrated into university classes and results will be featured in the National Snow and Ice Data Center?s Monthly Highlights. To communicate climate research to the general public, datasets created for this research will be formatted for Science on a Sphere technology. A research team member and the graduate student will present these data and their significance to the public as a part of science outreach shows at the University of Colorado?s Fiske Planetarium.

Technical

This is an effort to take advantage of data from a suite of advanced atmospheric reanalyses, satellite remote sensing and model experiments to address the characteristics, variability and environmental impacts of the Summer Arctic Frontal Zone (AFZ), and how this seasonal feature may change over the next century. Most prior research concludes that the AFZ develops primarily in response to summer heating contrasts between the Arctic Ocean and snow-free land. The AFZ is best developed along the Eurasian and Alaskan coasts, especially in Eastern Siberia and north of Alaska's Brooks Range, where it appears that temperature gradients are sharpened by topographic trapping of cold Arctic Ocean air. The AFZ at the surface is overlain by a jet-like feature at the tropopause. Areas where the AFZ are best expressed are regions of frequent cyclogenesis, and these cyclones have significant impacts on the summer precipitation regime not only along the Arctic coast, but also over the central Arctic Ocean, which is where many of the lows migrate into and decay. Migration of cyclones into the central Arctic Ocean also likely influences the sea ice state. This study will focus on: how seasonal development of the AFZ relates to variations in the seasonal timing of snow-free conditions over land, the location of the sea ice margin, surface temperatures, and topography; whether there is support for persisting views of ecological controls on the AFZ; how different patterns of atmospheric circulation influence the expression of AFZ; how variability in the AFZ is expressed in terms of patterns of cyclogenesis and summer precipitation; and how the AFZ will change through the 21st century in response to changes in seasonal snow cover, sea ice conditions and potential changes in atmospheric circulation patterns. The study will employ data from three atmospheric reanalyses, sea ice extent from the satellite passive microwave record, Reynolds sea surface temperature, satellite-derived terrestrial snow cover extent, experiments with the Weather Research and Forecasting regional model and output from coupled global models.

The Arctic Ocean is experiencing rapid and dramatic environmental changes related to global warming. These changes affect the arctic marine carbon cycle as part of complex and coupled system interactions between the ocean, atmosphere, cryosphere and land surfaces, with important feedbacks to the global Earth System, including altering the concentration of atmospheric greenhouse gases. Previous and ongoing studies have laid the foundations for improving the understanding of arctic carbon sinks and sources using observational studies, regional ice-ocean modeling, and recent global carbon cycle simulations. However, there remain large uncertainties in the understanding of variability and change in the arctic marine carbon budget that are difficult to reconcile with existing tools.

This project will use the Regional Arctic System Model, comprised of marine biogeochemistry components in the eddy-resolving ocean and sea ice models to advance understanding and prediction of the arctic biogeochemical system, including shelf-basin and vertical nutrient exchange, the subsurface chlorophyll maximum, ice edge and under ice blooms and their role in ecosystem response to climate change. It builds on the recent and ongoing research by the team of investigators, including the development and evaluation of the marine biogeochemistry components for global sea ice/ocean models and the high resolution Regional Arctic System Model. The model simulates mass and energy exchange between sea ice, ocean, atmosphere and land on decadal timescales, with regionally constrained variability using observationally based atmospheric and oceanic datasets at lateral boundaries. The research will: (i) evaluate and refine the established ocean marine biogeochemistry model, and (ii) add a newly developed sea ice algal biogeochemistry component within the existing model infrastructure. These model enhancements will help better quantify variability, complexity, and change in arctic marine primary production. The overarching goal of this study is to achieve a comprehensive understanding of interactions between physical system components and the arctic marine carbon cycle, and to advance arctic system prediction at seasonal to centennial time scales with quantified uncertainty.

Researchers seek to make high-resolution temporal and size distribution measurements of aerosol composition and size in the Ross Island region, coastal Antarctica. An Aerosol Mass Spectrometer (AMS) will be used to provide quantitative size and chemical mass loading information, in near real-time of non-refractory sub-micron aerosol particles such as sulfate, nitrate, chloride, ammonium, and organic carbon species. Additional measurements will include aerosol sizing with overlapping size ranges from 20 nm to 100 um, and particle into liquid sampling for bulk ionic compositional analysis of larger aerosol particles.

Advantages in continuous AMS monitoring of aerosol include being able to observe the episodic nature and short duration of new particle nucleation events, thus capturing the extreme variability of meteorological conditions expected in maritime Antarctica.

These aerosol measurements are likely to be of interest to other disciplines. Training of a post-doctoral associate, and research experience for a Polar-TREC participant are allied broader impacts.

Proposal Title: Collaborative Research: Seasonal Sea Ice Production in the Ross Sea, Antarctica (working title changed from submitted title)
Institutions: UT-San Antonio; Columbia University; Naval Postgraduate School; Woods Hole Oceanographic Institute; UC@Boulder

The one place on Earth consistently showing increases in sea ice area, duration, and concentration is the Ross Sea in Antarctica. Satellite imagery shows about half of the Ross Sea increases are associated with changes in the austral fall, when the new sea ice is forming. The most pronounced changes are also located near polynyas, which are areas of open ocean surrounded by sea ice. To understand the processes driving the sea ice increase, and to determine if the increase in sea ice area is also accompanied by a change in ice thickness, this project will conduct an oceanographic cruise to the polynyas of the Ross Sea in April and May, 2017, which is the austral fall. The team will deploy state of the art research tools including unmanned airborne systems (UASs, commonly called drones), autonomous underwater vehicles (AUVs), and remotely operated underwater vehicles (ROVs). Using these tools and others, the team will study atmospheric, oceanic, and sea ice properties and processes concurrently. A change in sea ice production will necessarily change the ocean water below, which may have significant consequences for global ocean circulation patterns, a topic of international importance. All the involved institutions will be training students, and all share the goal of expanding climate literacy in the US, emphasizing the role high latitudes play in the Earth's dynamic climate.

The main goal of the project is to improve estimates of sea ice production and water mass transformation in the Ross Sea. The team will fully capture the spatial and temporal changes in air-ice-ocean interactions when they are initiated in the austral fall, and then track the changes into the winter and spring using ice buoys, and airborne mapping with the newly commissioned IcePod instrument system, which is deployed on the US Antarctic Program's LC-130 fleet. The oceanographic cruise will include stations in and outside of both the Terra Nova Bay and Ross Ice Shelf polynyas. Measurements to be made include air-sea boundary layer fluxes of heat, freshwater, and trace gases, radiation, and meteorology in the air; ice formation processes, ice thickness, snow depth, mass balance, and ice drift within the sea ice zone; and temperature, salinity, and momentum in the ocean below. Following collection of the field data, the team will improve both model parameterizations of air-sea-ice interactions and remote sensing algorithms. Model parameterizations are needed to determine if sea-ice production has increased in crucial areas, and if so, why (e.g., stronger winds or fresher oceans). The remote sensing validation will facilitate change detection over wider areas and verify model predictions over time. Accordingly this project will contribute to the international Southern Ocean Observing System (SOOS) goal of measuring essential climate variables continuously to monitor the state of the ocean and ice cover into the future.

Arctic cyclones are an important contributor to sea ice deformation and oceanic mixing. Changes
in storm activity, and associated atmospheric feedbacks, have been linked to increased seasonality of the high north in the last decade, and with sea ice depletion during summer months. Cyclones are also likely to respond to changes in Arctic ice cover and ocean state indicating that
the atmosphere-ocean-ice system is tightly coupled through processes related to cyclones. Previous Arctic modeling studies typically used regional model simulations without full coupling
of the atmosphere-ocean-ice system, or fully coupled global climate models that do not permit year-on-year comparison with the observational record. This study will avoid such limitations by using
the Regional Arctic System Model (RASM), for which output corresponds directly with month-on-month observational records. This
will allow assessment of the ice-ocean-atmosphere coupling processes on multiple temporal
and spatial scales, and to relate them to limited Arctic Ocean measurements to build a more complete understanding of how increased cyclone activity may be helping to shift the surface climate of the Arctic to a new, warmer state with seasonal sea ice cover, and of how cyclones
will respond to this new Arctic Ocean state.

The impact of cyclones on Arctic stakeholder sectors in northern and western Alaska, including coastal communities and marine transport, will be assessed through a partnership with the Alaska Center for Climate Assessment and Policy and the project's inventory of Arctic cyclones and associated ocean and sea ice conditions will be archived at the National Snow and Ice Data Center. Historical time series of annual and seasonal Arctic cyclone activity, maps of tracks and intensities of Arctic cyclones, and case studies of intense or impactful cyclones will be made available on a project web page. The project will engage graduate students and a post-doctoral fellow,
and results will be used in atmospheric and oceanic science undergraduate and graduate level courses at the project institutions. Outcomes from this work will be address priorities in the US National Strategy for the Arctic Region and will address key uncertainties in understanding extreme events and their role in the Arctic climate system.

The recent loss of Arctic sea ice has increased the potential for ocean-atmosphere coupling
in the Arctic, especially in areas of low ice concentration or where the ice edge has receded. An important aspect of increased ocean-atmosphere Arctic coupling is the
 potential increase
of the ocean's response to storms. Where once mitigated by thick ice, wind-induced ice deformation and oceanic mixing are increasing as the ice pack thins. The decreasing Arctic ice cover and associated warming of the Arctic Ocean may also impact cyclone intensity and frequency. This grant will support investigation of changes in atmosphere-ice-ocean coupling in the presence of cyclones in the Arctic. It will advance our understanding of coupled atmosphere-ocean-ice processes with a focus on the role and response of cyclones in altering the state of the Arctic system. A cyclone tracking scheme will be applied to reanalyses, yielding an inventory of Arctic cyclone locations, tracks, and intensities that will provide a framework for analysis of ice and upper-ocean responses to storms. The responses of ice concentration, ocean temperature and salinity, and associated ice mass balance before, during, and after cyclones at a variety of intensities will be documented. The same analysis will be applied
to output from the high-resolution Regional Arctic System Model (RASM) and to output from
a suite of global climate models (GCMs). Using a novel set of metrics computed from the output of RASM, peak temporal and spatial scales of oceanic mixing, sea ice deformation, and turbulent fluxes associated with the passage of storms in the Arctic will be determined, in order to assess coupled cyclone-ocean-sea ice processes. Changes in the cyclone climatology between pairs of coupled RASM simulations, that differ only in sea ice and ocean state, and in current and end of the 21st century CMIP5 simulations will allow for assessment of cyclone response to changing ocean and ice state. This award is made by the Arctic Section of NSF Polar Programs and co-funded by the NSF GEO effort PREEVENTS.

The Antarctic Automatic Weather Station (AWS) network is the most extensive ground meteorological network in the Antarctic, approaching its 30th year at several of its installations. Its prime focus as a long term observational record is to measure the near surface weather and climatology of the Antarctic atmosphere. AWS stations measure air-temperature, pressure, wind speed and direction at a nominal surface height of ~ 2-3m. Other parameters such as relative humidity and snow accumulation may also be taken. Observational data from the AWS are collected via Iridium network, or DCS Argos aboard either NOAA or MetOp polar orbiting satellites and thus made available in near real time to operational and synoptic weather forecasters. The surface observations from the AAWS network are important records for recent climate change and meteorological processes. The surface observations from the AAWS network are also used operationally, and in the planning of field work. The surface observations made from the AAWS network have been used to check on satellite and remote sensing observations.

This project proposes to use the surface conditions observed by the AWS network to determine how large-scale modes of climate variability impact Antarctic weather and climate, how the surface observations from the AWS network are linked to surface layer and boundary layer processes, and to quantify the impact of snowfall and blowing snow events. Specifically, this project proposes to improve our understanding of the processes that lead to unusual weather events and how these events are related to large-scale modes of climate variability. This project will fill a gap in knowledge of snowfall distribution, and distinguishing between snowfall and blowing snow events using a suite of precipitation sensors near McMurdo Station.

This study will use an emerging technology, unmanned aircraft systems, to collect measurements with the goal of improving weather and climate models of the Arctic system. It is part of the international MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) program, an extensive field effort to freeze an icebreaker into sea ice for an entire year to serve as a research platform for a comprehensive study of the atmosphere, ocean and ice system in the high Arctic. The unique and potentially transformative aspect of this project is that unmanned aircraft collect data at small spatial and temporal scales, providing new information about variability in temperature, humidity, and winds. In addition, direct measurements of these variables over breaks in the sea ice have been very limited to date. Therefore, this study will address a significant source of error in our current ability to forecast how energy is transferred between the atmosphere and underlying ice and sea surface. Together with information from collaborating scientists participating in the MOSAiC field effort, the investigators will evaluate a series of hypotheses related to the performance of model simulations of key processes over the central Arctic Ocean. The investigators will also give pubic lectures at schools and other venues, capitalizing on interest and excitement in use of new technology though use of videos and photos of the unmanned aircraft systems. They will support training for early career scientists by involving graduate students and postdoctoral scientists.

The investigators will deploy an unmanned aircraft system to measure atmospheric temperature, winds, and humidity, as well as surface albedo. Flights will take place from mid-winter (February) through late summer (August) to capture variable conditions in both the atmosphere and sea ice surface and will include routine profiling of the lower atmosphere, spatial mapping of thermodynamic quantities and surface albedo, and mapping of the lower atmospheric structure over leads. This data will be evaluated with measurements of the atmosphere, ocean and ice collected by other scientists as part of the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) project to address hypotheses related to the performance of modeling tools in simulating key processes over the central Arctic Ocean. These include questions about sub-grid scale variability of atmospheric and surface parameters and its influence on model-simulated surface energy budget; the influence of leads in the sea ice on energy transfer from the ocean to the atmosphere and how models represent this transfer; and the importance of vertical resolution in simulation of the Arctic atmosphere and its impact on the simulation of clouds and the surface energy budget. The investigators will compare observations from unmanned aerial systems to a variety of simulations, ranging from global products to fully-coupled regional simulations completed using the Regional Arctic System Model (RASM) to detailed single-column and 2D modeling at high resolution.

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.

Despite several decades of successful Antarctic aviation, centered upon flight operations in the McMurdo (Phoenix Field, Ross Island; RsI) area, systemized description of radar observations such as are normally found essential in operational aviation settings are notably lacking. The Ross Island region of Antarctica is a topographically complex region that results in large variations in the mesoscale high wind and precipitation features across the region. The goals of this project are to increase the understanding of the three-dimensional structure of these mesoscale meteorology features. Of particular interest are those features observed with radar signals.

This project will leverage observations from the scanning X-band radar installed during the AWARE field campaign in 2016 and the installation of an EWR Radar Systems X-band scanning radar (E700XD) to be deployed during the 2019-20 field season, at McMurdo. Several science questions and case studies will be addressed during the season.

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.