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Level 1 Science Requirements Review

Level 1 Science Requirements Review. Science Objectives (following is from the draft project plan). What are the major forces and mechanisms causing the ice sheets to lose mass and change velocity, and how are these parameters changing over time?

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Level 1 Science Requirements Review

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  1. Level 1 Science Requirements Review

  2. Science Objectives(following is from the draft project plan) • What are the major forces and mechanisms causing the ice sheets to lose mass and change velocity, and how are these parameters changing over time? • How does the ice sheet/glacier bed topography, ice shelves/tongues, and grounding line configurations effect ice dynamics? • How does the bathymetry beneath ice shelves and the ocean/ice sheet interaction effect ice sheet/glacier flow dynamics? • What are yearly snow accumulation rates over the ice sheets and sea ice? • What is the snow depth on sea ice and how does snow depth affect the radiation and temperatures budgets in the Arctic? • What are projected declines in extent and thickness of the Arctic sea ice and how will these declines affect the ice albedo feedback in climate models?

  3. Ice Sheet Requirements • The objectives are: • To monitor changes in Greenland and Antarctic ice-sheet elevations during the gap in satellite coverage between ICESat-1 and ICESat-2. • To provide a dataset for cross-calibration and validation of ice-sheet elevations from satellite lidars (ICESat-1, ICESat-2, DesDynI-Lidar) and radars (CryoSat-2 and Envisat). • To provide a dataset for improving the ICESat-1 ice-sheet elevation time series, including better characterization of ICESat-1 errors. • To provide a dataset for improving numerical models of ice-sheet dynamics, especially maps of the bed beneath glaciers and ice shelves. • To provide a dataset for improving instrument simulation and performance analysis in support of future missions, such as ICESat-2 and DesDynI-Lidar. • To support, when feasible, field programs in Greenland and Antarctica.

  4. Ice Sheet Science requirements from the Existing Project Plan: • IceBridge shall make altimetry measurements that enable determination of surface elevation change to an uncertainty of 10 cm/yr over outlet glaciers of the Greenland and Antarctic ice sheets. • IceBridge shall make measurements that enable determination of surface slopes to an uncertainty of 0.5°. • IceBridge shall fly at least 250,000 total km per year, with 30,000 km per year specifically along ICESat-1 tracks over sea ice and land ice. • IceBridge shall fly at least 500 km per year as underflights along CryoSat-2 tracks over sea ice and land ice. • IceBridge shall, for at least two field seasons, make altimetry measurements along a swath of the southern limit of the ICESat-1 tracks, enabling direct comparisons of surface elevations for a large number of ICESat-1 tracks. • IceBridge shall make repeat altimetry measurements that enable determination of surface elevations, and surface elevation change, in critical areas where ICESat-1 data are limited or non-existent, including: • Coastal Greenland • Antartica’s Pine Island, Thwaites and Crane Glaciers • Amundsen Coast • Antarctic Peninsula • Accessible areas of East Antarctica • Accessible areas of the South Pole region not surveyed by ICESat-1  • IceBridge shall make radar measurements that enable mapping and characterization of the bedrock beneath land-based ice as follows: For Greenland: in consideration of existing data, to establish a 100 km by 100 km grid and provide 10 km by 10 km grids over five major outlet glacier catchments. For Antarctica, provide mapping over accessible outlet glaciers that improve numerical models of ice sheet flow according to the priorities in #4. • IceBridge shall make gravity measurements that enable the determination of bathymetry beneath ice shelves and sub-ice-sheet bedrock topography that cannot be mapped with radar for five key outlet glaciers in Greenland and accessible portions of Antarctica according to the priorities in #4. • IceBridge shall conduct flight experiments that enable the inter-calibration of the flight instruments and the characterization of their errors. • IceBridge shall in conjunction with altimetry measurements make measurements to determine the thickness and structure of the snow and firn layer.

  5. Glaciers from existing Project Plan IceBridge Mountain Glacier and Ice Cap Science Requirements • The objectives are: • To monitor changes in selected mountain glacier and ice-cap elevations during the gap in satellite coverage between ICESat-1 and ICESat-2. • To provide a dataset for cross-calibration and validation of glacier and ice-cap elevations from satellite lidars (ICESat-1, ICESat-2, DesDynI-Lidar) and radars (CryoSat-2 and Envisat). • To provide a dataset for improving the ICESat-1 ice-sheet elevation time series, including better characterization of ICESat-1 errors. • To improve our understanding of tidewater glacier dynamics and the role that they play in the stability of ice sheets. • To map the bed beneath selected mountain glacier and ice-caps. • Science requirements: • IceBridge shall provide annual surveys of the 50 most important glaciers and ice caps around the Arctic to sea level rise estimates. • IceBridge shall provide at least 15,000 km of centerline profiles along these glaciers and ice caps. • IceBridge shall provide swath maps with a 1-m x 1-m lidar point density, 500 meters wide, with a 30-cm vertical accuracy. • IceBridge shall provide at least 50 crossovers with CryoSat-2 and ICESat tracks.

  6. Sea ice from Existing Project Plan • The objectives are: • To monitor changes in Arctic Ocean sea ice freeboard and thickness during the gap in satellite coverage between ICESat-1 and ICESat-2. • To provide a dataset for cross-calibration and validation of freeboard and thickness estimates from satellite lidars (ICESat-1 and ICESat-2) and radars (Envisat and CryoSat-2). • To provide a dataset for understanding the snow depth distributions of the Arctic and Southern Oceans, and for improvements in thickness retrieval algorithms. • To understand the feasibility and limitations of sea ice thickness retrieval in the Southern Ocean ice cover from satellite lidar and radar freeboards. • To support, when feasible, field programs in the Arctic and Southern Oceans.

  7. Sea Ice Science Requirements from existing project plan: • IceBridge shall make surface elevation measurements that enable determination of sea-ice freeboard to an uncertainty of 5 cm at 500 m length scales. • IceBridge shall make elevation measurements of the air-snow and the snow-ice interfaces that enable the determination of snow depth to an uncertainty of 5 cm at 500 m length scales. • IceBridge shall provide annual acquisitions along near-exact repeat tracks during the late winters of the Arctic and Southern Oceans. • IceBridge shall provide capability, annually, to fly at least four 1500 km tracks during the late winter of the Arctic Ocean and at least four 1500 km tracks during the late winter of the Southern Oceans. The location of exact tracks shall be determined by the IceBridge Science Team. • IceBridge shall include flight tracks for sampling of the: • Perennial and seasonal ice covers between Greenland, the central Arctic, and the Alaskan Coast. • Multi-year sea ice pack north of Ellesmere and Greenland. • Sea ice across the Fram Strait flux gate. • Sea ice cover in Eastern Arctic North of the Fram Strait. • Bellingshausen Sea ice cover. • Weddell sea ice between tip of Antarctic Peninsula and Cap Norvegia. • Mixed ice cover in the western Weddell between the tip of Antarctic Peninsula and Ronne Ice Shelf. • CryoSat-2 ground tracks (coincident when possible).

  8. Points to Consider for the Updating Requirements • What are the complementary requirements in support of ICESat continuity including cross comparison with Cryosat? • What sorts of specific modeling questions are IceBridge data intended to support? What are the outstanding modeling/prediction questions that could be resolved with IceBridge data? • How should resources be partitioned between sea ice, ice sheets, ice caps, etc. • How should resource be partitioned between mission continuity, calibration, parameter measurements, process studies, modeling/prediction studies. • Does the science team have any requirement on instrument/configuration stability? When should instruments be upgraded? When should new instruments be added? Are all instruments routinely needed? • How are the total flight miles for science and Icesat continuity justified (other than cost) • Ice sheet surface slopes are usually less than 2 degrees, where does the 0.5 degree slope error come from? • Critical areas seem to ultimately encompass all of the Greenland and Antarctic ice sheets. Can this be refined? • Should there be requirements for gathering information about ice sheet basal conditions and processes at grounding line? • Why is ice sheet gridding specified for radar but not the other instruments? Where do the gridding requirements come from? Why not swath mapping? • What measurements are contributing to improved modeling of tidewater glaciers? What accuracy is required • What are the 50 most important glaciers to monitor? • Does the ATM provide 5 cm height accuracy for freeboard measurements? What is the requirement on ice thickness and is this consistent? • How successfully can an airborne program “To monitor changes in Arctic Ocean sea ice freeboard and thickness during the gap in satellite coverage between ICESat-1 and ICESat-2.” Select monitoring sites seem feasible but then what sort of modeling is required to extrapolate across the basin. • What does it mean to have a 5 cm accuracy on sea ice snow cover given the prevalence of snow layer flooding in the Antarctic? • What are the IceBridge success criteria?

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