Effects of Last Glacial Maximum (LGM) sea surface temperature and sea ice extent on the isotope–temperature slope at polar ice core sites

• Published in: Climate of the Past
• Main Authors: Cauquoin, Alexandre, Abe-Ouchi, Ayako, Obase, Takashi, Chan, Wing-Le, Paul, André, Werner, Martin
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Copernicus Publications 2023
• Subjects: Antarctic; Southern Ocean; West Antarctica; Greenland; Antarc*; Antarctica; EPICA; ice core; North Atlantic; Sea ice
• Online Access: https://epic.awi.de/id/eprint/57984/; https://epic.awi.de/id/eprint/57984/1/Cauquoin_et_al_2023.pdf; https://doi.org/10.5194/cp-19-1275-2023; https://hdl.handle.net/10013/epic.698abb3a-36c2-4a8b-b998-b769e4da6358

table water isotopes in polar ice cores are widely used to reconstruct past temperature variations over several orbital climatic cycles. One way to calibrate the isotope– temperature relationship is to apply the present-day spatial relationship as a surrogate for the temporal one. However, this method leads to large uncertainties because several fac- tors like the sea surface conditions or the origin and transport of water vapor influence the isotope–temperature temporal slope. In this study, we investigate how the sea surface tem- perature (SST), the sea ice extent, and the strength of the Atlantic Meridional Overturning Circulation (AMOC) affect these temporal slopes in Greenland and Antarctica for Last Glacial Maximum (LGM, ∼ 21 000 years ago) to preindus- trial climate change. For that, we use the isotope-enabled at- mosphere climate model ECHAM6-wiso, forced with a set of sea surface boundary condition datasets based on recon- structions (e.g., GLOMAP) or MIROC 4m simulation out- puts. We found that the isotope–temperature temporal slopes in East Antarctic coastal areas are mainly controlled by the sea ice extent, while the sea surface temperature cooling af- fects the temporal slope values inland more. On the other hand, ECHAM6-wiso simulates the impact of sea ice extent on the EPICA Dome C (EDC) and Vostok sites through the contribution of water vapor from lower latitudes. Effects of sea surface boundary condition changes on modeled isotope-emperature temporal slopes are variable in West Antarctica. This is partly due to the transport of water vapor from the Southern Ocean to this area that can dampen the influence of local temperature on the changes in the isotopic compo- sition of precipitation and snow. In the Greenland area, the isotope–temperature temporal slopes are influenced by the sea surface temperatures near the coasts of the continent. The greater the LGM cooling off the coast of southeastern Green- land, the greater the transport of water vapor from the North Atlantic, and the larger the ...