The Antarctic palaeo record and its role in improving predictions of future Antarctic Ice Sheet change

Abstract

This paper reviews the ways in which the palaeo record of Antarctic Ice Sheet change can be used to improve understanding of contemporary ice sheet behaviour, and thus enhance predictions of future sea‐level change. The main areas where the palaeo ice sheet record can contribute are understanding long‐term ice sheet trajectory; providing data against which ice sheet models can be tested; to identify and understand the range and types of natural ice sheet behaviour; to balance the global water budget; to correct contemporary glaciological measurements of mass change; and to understand the relationship between polar ecosystems and the ice sheet. I review each in turn and argue that research priorities include understanding past West Antarctic Ice Sheet collapse and its timing; a focus on the palaeo record of rapid retreat events and how these unfolded in the geological past; improving the number and range of ice sheet reconstructions, particularly through the Holocene; continuing to investigate the potential for using sediments and landforms to parameterise basal conditions in ice sheet models; and understanding past East Antarctic Ice Sheet dynamics, particularly the evidence for partial deglaciation. Copyright © 2009 John Wiley & Sons, Ltd.

Sea-level rise due to polar ice-sheet mass loss during past warm periods

“…Rates of GMSL rise slowed by ~7 ka following the final deglaciation of the Laurentide Ice Sheet-from ~15 m kyr -1 between ~11.4-8.2 ka to ~1 m kyr -1 or less for the remainder of the pre-Industrial Holocene (82). Only a few meters of ice-sheet loss occurred between ~7 and ~2 ka (82,83), which is thought to be dominated by loss from the AIS (84,85). Field data and ice-sheet models suggest that the GrIS was smaller than present during the early to middle Holocene thermal optimum (9.5-5.5 ka) (86,87), and began to readvance during the cooler Neoglacial period (<5 ka), reaching its maximum extent in many places during the Little Ice Age and causing a GMSL lowering of <0.2 m (88).…”

“…2i) that reflect ice-sheet loss and coupled atmosphere-ocean variability (95). Late-Holocene ice-margin reconstructions for the AIS suggest little change (84,85,96), while those for the GrIS suggest general advance (86)(87)(88). The clearest signal in geological and long tide gauge records is the transition from low rates of change during the last ~2 ka (order tenths of mm yr -1 ) to modern rates (order mm yr -1 ) in the late 19 th to early 20 th centuries, although the spatial manifestation of this change is variable (1, 81).…”

“…4). The planktic  18 O from the Red Sea (15,75,84) is an innovative approach to overcoming some of the limitations of the benthic Constraining the total volume and geographic extent of grounded ice during the Last Glacial Maximum (LGM), in particular, is an important parameter for GIA model predictions of RSL across all time periods, including the present and past interglacial periods (e.g., 18).…”

Progress in modelling and observing Antarctic glacial isostatic adjustment

“…Given the continuing dominance of uncertainty in ice history, the most valuable data types for constraining GIA modelling are those that provide dated limits on ice extent, such as cosmogenic exposure dating of rock outcrops (Bentley 2010), ice cores (Lorius et al 1984) and marine geophysics (Cofaigh et al 2008, Livingstone et al 2012). Figure 2b also shows locations of existing LGM ice-extent data as tabulated by Whitehouse et al (2012a); figure 2d shows the locations for the 5 ka Before Present (BP) time slice.…”

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“…It is unclear, however, whether the current ice loss results from ongoing deglaciation since the Last Glacial Maximum (LGM) (e.g., Bentley, 2010), recent climatic/oceanographic warming, or recent internal ice sheet dynamics (Joughin and Alley, 2011;Joughin et al, 2012). If the WAIS has undergone similar thinning and retreat in the past, the factors driving that retreat can be compared to modern conditions.…”