Enhancing NASA's Contributions to Polar Science A Review of Polar Geophysical Data Sets (2001) / Chapter Skim
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3. Science -Driving Questions: The Polar Regions in the Context of NASA's Earth Science Enterprise
3. Science -Driving Questions: The Polar Regions in the Context of NASA's Earth Science Enterprise
Pages 44-71
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From page 44... ...
Specific, measurable biogeophysical phenomena are the focus; for example, to understand climate variability over land, researchers must be able to characterize individual elements of the Arctic water cycle such as seasonal variations in permafrost, soil moisture, evapotranspiration, precipitation minus evaporation, surface temperature, runoff, and snow cover. Each of the five ESE science questions is addressed in a section below.
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From page 45... ...
The committee elected to begin with the definition used by the WCRP's Climate and Cryosphere Program, which defines the cryosphere as that portion of the Earth containing sea ice, snow cover, permafrost, ice sheets, and glaciers (WCRP, 2000~. The committee also included critical processes that influence surface energy, freshwater fluxes in the cryosphere, and carbon and trace gas exchanges at the atmospheric interface.
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From page 46... ...
One important aspect of the debate on climate change centers around the presumed intensification of the global water cycle through which excess energy trapped as a consequence of the greenhouse effect is transformed into an increase in the poleward delivery of water vapor and heat by atmospheric transport. Recent observational evidence shows an increase of storm tracks across the polar front and changes in precipitation patterns associated with the North Atlantic Oscillation (NAO)
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From page 47... ...
Measurements of changes in ice sheet elevation are not of themselves diagnostic of the processes that are producing change, but the measurements are nearly directly translatable into a component of present sea level rise. Recent NASA PARCA results showing a decrease in the overall mass of the Greenland ice sheet over the last five years is the first reliable indication of the impact of the ice sheets on global sea level rise, there is a clear need to continue this time series and provide similar information for the Antarctic.
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From page 48... ...
1.2c In West Antarctica, are the present local imbalances, caused by flow variations in large outlet glaciers and ice streams and possibly by local accumulation variations, consistent with long-term retreat or possible instability? Rapid ice discharge in large outlet glaciers and ice streams carries much of the mass lost from the large ice sheets.
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From page 49... ...
The resultant freshening might influence the strength and location of deep water formation in the North Atlantic Ocean. Measurement Requirements: Precipitation, river runoff, snow cover, glacial runoff, ocean circulation, temperature, and salinity.
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From page 50... ...
Ice edge productivity is a primary source of productivity in the polar oceans that is particularly sensitive to warming. Projected reductions in sea ice concentration, enhanced light availability, and increased water temperatures can increase algal productivity.
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From page 51... ...
Drainage basins provide a useful organizing framework for tracking water, energy, and biogeochemical fluxes associated with the terrestrial hydrological cycle. When the Arctic is considered from the standpoint of a contributing drainage area to the Arctic Ocean, it constitutes the most land-dominated of all ocean basins with the greatest impact from freshwater discharge.
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From page 52... ...
2: Primary Forcings of the Polar Climate System What are the major fluxes of CO2 and other trace gases from the polar land surfaces and oceans? The exchange of carbon and trace gases from polar ecosystems is regulated by a host of complex processes.
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From page 53... ...
Measurement Requirements: Sea ice concentration and extent, evapotranspiration, soil moisture, surface temperature, permafrost characteristics, vegetation characteristics, disturbance characteristics, wetland extent, CO2 and CH4 Jquxes, nitrogen deposition, river discharge, and chemistry. 2.2 What are the spatial and temporal distributions and variability of aerosols in the polar atmosphere?
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From page 54... ...
Projected increases in winter precipitation in high latitudes may or may not be balanced against increases in evaporation associated with elevated air temperatures, thus making the corresponding changes in ice mass difficult to predict. Whether the ice sheets are responding primarily to recent forcings or to longer-timescale forcings (i.e., are the ice sheets in balance with the recent climate)
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From page 55... ...
Measurement Requirements: Sea ice concentration, thickness, and velocity; precipitation; evaporation; river runoff; sea surface height; and ocean temperature and salinity, and circulation. What is the relationship between polar ocean circulation and the large-scale interrannual and decadal modes of atmospheric variability (e.g., E1 Nino Southern Oscillation, Arctic Oscillation, North Atlantic Oscillation, Antarctic Oscillation)
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From page 56... ...
Measurement Requirements: Surface albedo, sea ice concentration and thickness, melt-pond fraction, snow depth on sea ice, and surface temperature. 3.3b How is the albedo-temperature feedback affected by polar clouds and aerosols?
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From page 57... ...
An important connection between the ocean surface and overlying atmosphere in the polar regions is defined by the state of sea ice, both in terms of its extent and surface radiation budget. Sea ice can be viewed both as a source of water vapor through sublimation and as regulator of the amount of open Arctic Ocean water exposed to
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From page 58... ...
Measurement Requirements: Atmospheric temperature and humidity profiles, cloud and vertical layer structure, wind profiles and advective fluxes, surface turbulent fluxes, surface temperature, and salinity. What role does the cryosphere play in determining the dependence of the large-scale atmospheric circulation on the global meridional temperature gradient?
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From page 59... ...
, and surface and atmospheric radiative fluxes, and precipitation. 3.8 How will land surface hydrology and energy exchanges be influenced by the climate-induced changes to vegetation structure and distribution across the polar regions?
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From page 60... ...
Measurement Requirements: Vegetation characteristics, albedo, snow characteristics, precipitation, evapotranspiration, disturbance characteristics, permafrost characteristics, soil moisture, river runoff, rainfall, snowfall, and snow cover. Issue No.
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From page 61... ...
Measurement Requirements: Permafrost extent, thermokarst topography, soil temperature profile, land-surface temperature, snow characteristics, soil moisture, vegetation characteristics, disturbance characteristics, wetlands extent. How will changes in coastal sea ice-coverage and sea-level rise affect stone surges, coastal erosion, and inundation of the coastal freshwater supply?
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From page 62... ...
Measurement Requirements: Precipitation, snow cover, ground water, and river runoff. How will shipping, offshore mineral extraction, commercialfishing, and subsistencefishing and hunting be impacted by changes in coastal sea ice characteristics?
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From page 63... ...
Measurement Requirements: Permafrost characteristics, vegetation characteristics, rainfall, snowfall, snow characteristics, disturbance characteristics, wetlands extent, soil moisture, land surface temperature, photosynthetically active radiation, evapotranspiration, vegetation characteristics, sea ice extent and thickness, ultra-violet radiation, and sea surface temperature, salinity, and color. 4.6 How will changes in growing season and primary production influence agriculture and forestry in high-latitude regions, including disturbed regimes (e.g., fire, insects)
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From page 64... ...
, wetlands extent, soil moisture, land surface temperature, photosynthetically active radiation, and evapotranspiration. Issue No.
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From page 65... ...
5.3 What improvements to formulations of polar processes (e.g., sea ice, land surface energy exchanges) are necessary for the accurate simulation and prediction of climate and climate change?
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From page 66... ...
(B) Sea Ice and Ocean Models Assimilation and Initialization: Surface radiation fluxes; surface air temperature; humidity; winds and pressure; precipitation; ice concentration, thickness, and velocity; ocean temperature; salinity; and currents.
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From page 67... ...
: Ice sheet velocity, runoff or discharge, Yinternal la er distribution (D) Land System Models for Hydrology and Terrestrial Ecosystem Dynamics Assimilation and Initialization: Surface elevation and topography, precipitation, surface radiation flux components, surface temperature and albedo, surface air temperature, humidity and winds, vegetation characteristics, river and lake morphology, soil moisture, permafrost extent and temperature profiles, snow cover.
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From page 68... ...
Four classes of models are crucial for progressing in polar system science: ice sheet models, sea and ice ocean models, operational weather prediction models, and terrestrial hydrology and ecosystem dynamics models. The complexities of feedbacks within and among these realms requires a major synthesis effort.
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From page 69... ...
radius 1 3,6,7 Aerosol properties -Concentration 1 2 3 -Size distribution 1 2 3 -Refractive index 1 2 3 Surface temperature 1,2,4 1,2,3,4,5,6 5 A,B,C,D Surface albedo 1 3,4 B,C,D Surface pressure Surface heat flux -Radiation flux 1,2,4 1,7 B,C,D -Sfc air temp 2,4 1,6 B,C,D -Sfc winds 2,4 1,5,6 4 B,C,D -Sfc air humidity 2,4 1,5,6 B,C,D Precipitation -Rainfall 1,2,3,4 7,8,9 5 A,B,D -Snowfall 1,2,3,4 1,4,7,8,9 5 A,B,C,D CO2 Flux 3 1 CH4 Flux 3 1 Sfc UV radiation Permafrost -Extent 4 8,9 1,5,6 D -Freeze/thaw dates 4 8,9 1,5,6 -Temperature profile 4 8,9 1,5,6 D -Thermokarst topog 4 8,9 1,5,6 Land snow characteristics -Cover 4,8,9 3,5 D -Depth 8,9 3,5 -Water Equivalent 8,9 3,5 continues
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From page 70... ...
-Type 4 8,9 1,5 -Timing 4 8,9 1,5 -Extent 4 8,9 1,5 -Severity 4 8,9 1,5 River runoff 3 1 9 3 Ice sheet -Elevation 2 1 C -Thickness 2 C -Velocity 2 C -Discharge 2 1,2 C -Runoff 2 1,2 C S ea Ice -Concentration 3 1 2,3,4,5 2,4,5 A,B -Thickness 3 2,3 4,5 B -Velocity 3 B -Snow cover 3,5 B -Melt pond cover 3 Ocean -Temperature, salinity 3 -Currents 3 2,6 2 -Surface height ~ -Color (productivity)
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From page 71... ...
For example, A in column 5 corresponds to numerical weather prediction models. Examination of the number of times that a specific variable is cited under the various science questions provides a crude measure of the priority of need for measuring that variable.
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