Analysing the timing of peak warming and minimum winter sea-ice extent in the Southern Ocean during MIS 5e. (1st February 2020) - Chadwick, M.
Abstract: The peak of the Last Interglacial, Marine Isotope Stage (MIS) 5e (130–116 ka), provides a valuable 'process analogue' for validating the climatic feedbacks and forcings likely active under future anthropogenic warming. Reconstructing exact timings of MIS 5e peak warming and minimum winter sea-ice extent (WSIE) throughout the Southern Ocean (SO) will help to identify the interactions and feedbacks within the ice-ocean system. Here we present a new MIS 5e marine sediment record from the SW Atlantic sector together with 28 published core records (chronologies standardised to the LR04 δ 18 O benthic stack; Lisiecki and Raymo, 2005) to investigate the timing and sequence of minimum WSIE and peak warming across the SO. Sea-surface temperatures (SSTs) peaked earliest in the Indian (20 o E–150 o E) and Atlantic (70 o W–20 o E) sectors, at 128.7 ± 0.8 ka and 127.4 ± 1.1 ka respectively, followed by the Pacific sector (150 o E–70 o W) at 124.9 ± 3.6 ka. The interval of minimum WSIE for all three sectors occurred within the period from 129–125 ka, consistent with the ∼128 ka sea salt flux minimum in Antarctic ice cores. Minimum WSIE appears to have coincided with peak July insolation at 55 o S, suggesting it could be linked with the mildest winters. The reduced WSIE during MIS 5e would have likely reduced the production of deep- and bottom water masses, inhibiting storage of CO2 in the abyssal ocean and lowering nutrient availability in SO surface waters. Examining a wide spatial range of proxy records for MIS 5e is a critical step forward in understanding climatic interactions and processes that will be active under warmer global temperatures. Highlights: MIS 5e peak sea-surface temperatures occur synchronously in the Indian and Atlantic sectors. The Pacific sector reaches maximum sea-surface temperatures later than the Indian and Atlantic sectors during MIS 5e. MIS 5e minimum winter sea ice extent occurs synchronously throughout the Southern Ocean.