Preprints
https://doi.org/10.5194/egusphere-2023-850
https://doi.org/10.5194/egusphere-2023-850
09 May 2023
 | 09 May 2023

Glacial-interglacial Circumpolar Deep Water temperatures during the last 800,000 years: estimates from a synthesis of bottom water temperature reconstructions

David M. Chandler and Petra M. Langebroek

Abstract. Future climate and sea-level projections depend sensitively on the response of the Antarctic Ice Sheet to ocean-driven melting and the resulting freshwater fluxes into the Southern Ocean. Incursion of Circumpolar Deep Water (CDW) across the Antarctic continental shelf, and into cavities beneath ice shelves, is increasingly recognised as a crucial heat source for ice shelf melt. Quantifying past changes in the temperature of CDW is therefore of great benefit for modelling ice sheet response to past warm climates, for validating paleoclimate models, and for putting recent and projected changes in CDW temperature into context. Here we synthesise the few available bottom water temperature reconstructions representative of CDW and its principal source water mass (North Atlantic Deep Water) over the past 800 kyr. Estimated CDW temperature anomalies consistently reached ca. −2 °C during glacial periods, warming to +0.1 to +0.5 °C during the strongest interglacials (marine isotope stages MIS 11, 9, 5, and 1). The temperature anomaly in MIS 7 was comparatively cooler at ca. −0.6 °C. Despite high variance amongst a small number of records, and poor (4 kyr) temporal resolution, we find persistent and close relationships between our estimated CDW temperature and Southern Ocean sea-surface temperature, Antarctic surface air temperature, and global ocean temperature reconstructions at glacial cycle time scales. Given the important role that CDW plays in connecting the world's three main ocean basins, and in driving Antarctic Ice Sheet mass loss, additional temperature reconstructions targeting CDW are urgently needed to increase temporal resolution and to decrease uncertainty in past CDW temperatures – whether for use as a boundary condition, model validation or in their own right.

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David M. Chandler and Petra M. Langebroek

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-850', Anonymous Referee #1, 26 Jun 2023
    • AC1: 'Reply to RC1 and RC2', David Chandler, 25 Aug 2023
  • RC2: 'Comment on egusphere-2023-850', Anonymous Referee #2, 04 Jul 2023
    • AC2: 'Reply to RC1 and RC2', David Chandler, 25 Aug 2023
David M. Chandler and Petra M. Langebroek
David M. Chandler and Petra M. Langebroek

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Short summary
Sea-level rise and global climate change caused by ice melt in Antarctica is a puzzle of feedbacks between the climate, ocean and ice sheets, over tens to thousands of years. Antarctic Ice Sheet melting is caused mainly by warm deep water from the Southern Ocean. Here, we analyse close relationships between deep water temperatures and global climate in the last 800,000 years. This knowledge can help us to better understanding how climate and sea-level are likely to change in the future.