Mid-Term Assessment of Progress on the 2015 Strategic Vision for Antarctic and Southern Ocean Research (2021) / Chapter Skim
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2 Priority I: Changing Antarctic Ice Sheets
2 Priority I: Changing Antarctic Ice Sheets
Pages 25-54
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From page 25... ...
noted that global mean sea level "is rising, with acceleration in recent decades due to increasing rates of mass loss from the Greenland and Antarctic ice sheets (very high confidence) ." In particular, the IPCC report stated that uncertainty in global sea level rise by 2100 is "mainly determined by the ice sheets, especially in Antarctica." Regions considered especially vulnerable are the Amundsen Sea embayment (including Thwaites Glacier; see Figure 2-1)
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From page 26... ...
, are needed to constrain the range of future sea level projections and will explicitly test whether the processes hypothesized to lead to high rates of ice mass loss actually occurred and whether they are accurately parameterized in models. Progress in advancing the Changing Antarctic Ice Sheets Initiative is discussed in this chapter, along with key implementation challenges and opportunities to improve progress toward the research goals.
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From page 27... ...
Priority I, Component i Component i of Priority I represents "a multidisciplinary initiative to understand why the Antarctic ice sheets are changing now and how they will change in the future." Building from the West Antarctic Ice Sheet (WAIS) Initiative,2 NASEM (2015)
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From page 28... ...
The report, however, did recommend that NSF should seek additional funding for this research, given the magnitude of the task and the projected costs of adaptation to sea level rise, which are orders of magnitude greater than funding currently provided for this research. Overall, Priority I, Component i, among the NASEM (2015)
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From page 29... ...
aims to reduce model uncertainty in projections of the glacier's evolution and sea level rise using coupled ice and ocean models. FIGURE 2-3 The eight International Thwaites Glacier Collaboration projects are designed to improve the understanding of key processes affecting the evolution of the Thwaites Glacier as well as historical context, thereby improving existing models and sea level rise predictions.
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From page 30... ...
Other ongoing non-ITGC projects and research avenues are critical to the science goals of Priority I, Component i. Airborne geophysical surveys with improved sensor technologies and ground penetrating radars are crucial for high-resolution mapping of bedrock elevation beneath ice sheets, inferring subglacial hydrology, imaging ice-shelf basal morphology crevasse characteristics, and quantifying accumulation rates and ice-shelf basal melt (see Figure 2-5)
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From page 31... ...
Terrestrial seismic data are critical in constraining geothermal heat flux and ice dynamics. Longer time series and expanded geographic coverage of POLENET, particularly in East Antarctica, would further reduce GIA uncertainties, provide supplementary evidence for ongoing mass changes, and establish how ice sheet–solid earth interactions influence ice sheet stability and sea level contributions (see Box 2-2)
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From page 32... ...
. Although the ITGC focuses on the most important vector of rapid sea level rise at present, the prospect of changes in the large marine-based East Antarctic glacial catchments may have larger implications for future sea level rise, as is outlined in Box 2-3.
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From page 33... ...
Understanding these interactions is particularly important in West Antarctica and some East Antarctic regions where the ice sheet is vulnerable to rapid climate-induced retreat and marine ice sheet instabilities. Advancing understanding of the coupled evolution of the Antarctic ice sheet and solid earth change requires a broadly interdisciplinary approach with close integration of observational and modeling studies to quantify the degree to which solid earth processes might moderate the response of the Antarctic ice sheet to future climate change or increase future sea level rise.
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From page 34... ...
The southward movement of strengthening westerly winds also pushes warm waters toward East Antarctica's continental shelves (Abram et al., 2014; Spence et al., 2014, 2017; Greene et al., 2017) , suggesting the potential for a significant contribution to sea level rise from this sector of East Antarctica in the decades to centuries to come.
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From page 35... ...
Antarctic research program but is not necessarily commensurate with the scope, breadth, and urgency of Priority I.i science. To put the funding into context, projected costs of adaptation of vulnerable, large cities to sea level rise range in the billions of dollars per city (e.g., MacOr, 2021)
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From page 36... ...
science community, organized for over two decades as the WAIS Initiative. WAIS Initiative science plans from 2002, 2014, and 2016 all outlined multidisciplinary research programs aimed at understanding ice sheet stability and projections of the contributions of the WAIS to current and future sea level rise.
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From page 37... ...
The projects are also enhanced by involvement of collaborators from Korea, Germany, and Sweden. Additionally, airborne surveys in East Antarctica have been conducted in coordination with Australia and China; the results of initial surveys are coming out (Cui et al., 2020)
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From page 38... ...
science programs, including the SCAR Instabilities and Thresholds in Antarctica (INSTANT) research program, which aims to quantify the Antarctic ice sheet contribution to past and future global sea level change, and the SCAR RINGS Action Group, which aims to map bed topography and grounding zone position around the circumference of the Antarctic ice sheet coastal margin, both key to advancing Priority I science objectives.5 The success of existing efforts indicates the critical role of partnerships with national and international agencies to bridge technology gaps and provide access to remote locations.
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From page 39... ...
Together, these datasets can be used to refine glaciological models essential for furthering the understanding of when and how the WAIS retreated and to estimate its past sea level contributions. Although NSF has focused on pursuing the scientific questions promoted in Priority I, currently funded projects addressing Priority I.ii science questions are limited in scope, geography, and funding (see Figure 2-7)
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From page 40... ...
Projects to cosmogenically date past ice extent in Antarctica have been funded since 2015 and are documenting ice retreat rates and drivers for ice sheet change around the Ross Embayment (e.g., Kingslake et al., 2018; Shakun et al., 2018; Balter-Kennedy et al., 2020)
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From page 41... ...
Unlike climate records preserved in continuous deep-sea sedimentary sequences, sediments from Antarctica's continental margins are unique in that they contain the only direct records of past ice advance and retreat, as well as windows into past climate and ocean change proximal to the Antarctic continent. Because of glacial processes, continental margin sediment sequences are, by their very nature, discontinuous.
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From page 42... ...
Scientific Community In terms of community, there has not yet been a specific effort by NSF or NSF-funded Antarctic researchers to bring together the different Antarctic-centric paleoclimate communities addressing past ice sheet change. There are encouraging signs of community building among the ice core researchers associated with 6 These facilities receive and curate marine sediment samples, rocks, and their associated data and metadata, enforce moratorium access, and are working toward providing up-to-date searchable databases.
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From page 43... ...
Collaboration with international programs, including IODP, has offered NSF an opportunity to leverage large field program investments by supporting post-expedition science. Between 2018 and 2019, three IODP expeditions were conducted in Antarctic waters as part of an ongoing initiative to address IODP scientific challenges complementary to those outlined in Priority I.ii, including How do ice sheets and sea level respond to a warming climate?
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From page 44... ...
The societal urgency of sea level rise necessitates that Antarctic researchers and their funding agencies broaden the geographic scope to more holistically address Priority I science questions. Such an effort would require substantially increased resources, as initially stated in NASEM (2015)
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From page 45... ...
is required for any marine access in remote West and East Antarctica, and three recent cruises of the vessel have been dedicated for ITGC activities.7 To address Priority I science questions, researchers must be able to access the inner continental shelf, which is complicated by icebergs, multiyear landfast ice,8 and sea ice. While the Nathaniel B
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From page 46... ...
In light of the enormity of the science objectives, the societal utility of the research findings, and COVID-19-related delays, continuation of international Thwaites Glacier region research with a second phase of 5 more years should be considered so that its research activities and goals can be completed. A range of research, discussed under the sections on Progress Toward Science Goals, that supplements ITGC projects also needs to be supported to more fully understand future WAIS change and sea level contributions.
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From page 47... ...
Such a field campaign could include marine to land-based geophysical surveys and in situ measurements; marine sediment, terrestrial bedrock, and ice core drilling; and atmosphere, ice surface, and oceanographic studies. Such a campaign would serve Priority I.i and I.ii and inform our nation and society about the risks of rapid sea level rise from East Antarctica, complementing the new understanding of sea level contributions of the Amundsen Sea Embayment sector of West Antarctica from the ITGC.
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From page 48... ...
Understanding the sub-ice-shelf environment is key to understanding changes in the marine-based parts of the ice sheets. The scientific community emphasized the need for increased technological capabilities for subice-shelf exploration to significantly advance science, including Argo float capabilities for critical information about the water column, AUV technologies for access to the sub-ice-shelf environment and crossing grounding lines, and seabottom transponder arrays for the navigation of AUVs under sea ice and ice shelves and for the positioning of floats during the ice-covered winter season.
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From page 49... ...
The advantages in investing in facilities to collect longer-term data are that they becomes immediately available to anyone who needs them and bypasses the need to go through complicated data sharing procedures. Coupled Ice Sheet–Ocean–Solid Earth and Climate Modeling Improvements in sea level rise projections require additional development of continental-scale coupled ice sheet–ocean–atmosphere–sea ice and solid earth models.
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From page 50... ...
East Antarctica is an important target in the coming years because of its potential contribution to sea level rise. Coastal East Antarctica is difficult to access logistically from U.S.
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From page 51... ...
To more fully address the major science objectives of Priority I, NSF should consider expanding initiatives beyond the International Thwaites Glacier Collaboration to include the Wilkes Land sector of East Antarctica. Multiple studies since 2015 have demonstrated that parts of East Antarctica are rapidly losing mass and have a greater potential for contributions to sea level rise than West Antarctica.
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From page 52... ...
Increased investments in new technologies, such as underwater robotics, will provide critical data and enhance the understanding of ice–ocean interactions at grounding lines. NSF should issue a specific call for proposals directed toward increasing knowledge of past ice sheet behavior, rates of change, and climate forcings -- information essential to place ongoing environmental change in context and accurately predict future sea level rise.
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From page 53... ...
Priority I: Changing Antarctic Ice Sheets 53 continue support for research to improve coupled atmosphere–ocean–ice–earth models, which need substantial additional development and data to improve parameterizations of important processes into an Earth system modeling framework. Specific calls for workshops and other initiatives that bring together terrestrial, marine, and modeling communities interested in studying past and ongoing change in key marine-based catchments in both West and East Antarctica are also recommended.
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