Abstract
ABSTRACTThe Holocene climatic optimum was a period 8–5 kyr ago when annual mean surface temperatures in Greenland were 2–3°C warmer than present-day values. However, this warming left little imprint on commonly used temperature proxies often used to derive the climate forcing for simulations of the past evolution of the Greenland ice sheet. In this study, we investigate the evolution of the Greenland ice sheet through the Holocene when forced by different proxy-derived temperature histories from ice core records, focusing on the effect of sustained higher surface temperatures during the early Holocene. We find that the ice sheet retreats to a minimum volume of ~0.15–1.2 m sea-level equivalent smaller than present in the early or mid-Holocene when forcing an ice-sheet model with temperature reconstructions that contain a climatic optimum, and that the ice sheet has continued to recover from this minimum up to present day. Reconstructions without a warm climatic optimum in the early Holocene result in smaller ice losses continuing throughout the last 10 kyr. For all the simulated ice-sheet histories, the ice sheet is approaching a steady state at the end of the 20th century.
Highlights
Simulating the past, present and future state of the Greenland ice sheet is important in the light of the recent rapid changes of the ice sheet and the potential sea-level contribution from a decreasing Greenland ice sheet (e.g. Rignot and others, 2011; Moon and others, 2012; Shepherd and others, 2012)
The results show that forcing an ice-sheet model with temperature reconstructions that contain a Holocene climatic optimum that has a sustained period where the temperatures are above present-day values lead to a minimum in ice sheet volume in the early to mid-Holocene
It was further found that applying temperature reconstructions without a Holocene climatic optimum, for example as used in the SeaRISE assessment (Bindschadler and others, 2013), leads to a continued mass loss through the Holocene, approaching a steady state in the late Holocene and the smallest ice volume is reached at present day
Summary
Simulating the past, present and future state of the Greenland ice sheet is important in the light of the recent rapid changes of the ice sheet and the potential sea-level contribution from a decreasing Greenland ice sheet (e.g. Rignot and others, 2011; Moon and others, 2012; Shepherd and others, 2012). This has motivated several modelling efforts investigating the future evolution of the ice sheet (e.g. Bindschadler and others, 2013; Goelzer and others, 2013; Vizcaino and others, 2015). The conversion from the isotope records to past temperatures remains a non-trivial task due to several processes, such as seasonality of precipitation events and changes in the conditions of the vapour source regions, affecting the isotopic signal and leading to different sensitivities between δ18O and temperature for different climate regimes (Jouzel and others, 1997; Gkinis and others, 2014)
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