Abstract
Abstract. The DCESS (Danish Center for Earth System Science) Antarctic Ice Sheet (DAIS) model is presented. Model hindcasts of Antarctic ice sheet (AIS) sea level equivalent are forced by reconstructed Antarctic temperatures, global mean sea level and high-latitude, ocean subsurface temperatures, the latter calculated using the DCESS model forced by reconstructed global mean atmospheric temperatures. The model is calibrated by comparing such hindcasts for different model configurations with paleoreconstructions of AIS sea level equivalent from the last interglacial, the last glacial maximum and the mid-Holocene. The calibrated model is then validated against present estimates of the rate of AIS ice loss. It is found that a high-order dependency of ice flow at the grounding line on water depth there is needed to capture the observed response of the AIS at ice age terminations. Furthermore, it is found that a dependency of this ice flow on ocean subsurface temperature by way of ice shelf demise and a resulting buttressing decrease is needed to explain the contribution of the AIS to global mean sea level rise at the last interglacial. When forced and calibrated in this way, model hindcasts of the rate of present-day AIS ice loss agree with recent, data-based estimates of this ice loss rate.
Highlights
The Antarctic ice sheet is a major player in the earth’s climate system and is by far the largest depository of fresh water on the planet
Ice stored in the Antarctic ice sheet (AIS) contains enough water to raise sea level by about 58 m, and ice loss from Antarctica contributed significantly to sea level high stands during past interglacial periods (Vaughan et al, 2013; Kopp et al, 2009; Naish et al, 2009)
I formulated a simple Antarctic ice sheet model by first adopting and making corrections to a published mass balance approach (Oerlemans, 2003, 2004, and 2005) and by advancing a new treatment of ice flow at the grounding line based on recent advances in our understanding of the controls on this flow
Summary
The Antarctic ice sheet is a major player in the earth’s climate system and is by far the largest depository of fresh water on the planet. There is considerable uncertainty as to the amount the AIS will contribute to future sea level change in response to ongoing global warming (Church et al, 2013). A broad hierarchy of AIS models have been developed and applied to try to understand the workings of the AIS and to form a robust basis for future projections of the AIS contribution to sea level change (e.g., Huybrechts, 1990; Huybrechts and de Wolde, 1999; Oerlemans, 2003; Pollard and De Conto, 2009; Whitehouse et al, 2012). A common feature of many of these models is an increase in AIS ice mass in response to warming. This is a consequence of increased snowfall as warming leads to more precipitable water in the atmosphere that falls as snow for cold Antarctic temperatures.
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