Abstract
Deglacial transitions of the middle to late Pleistocene (terminations) are linked to gradual changes in insolation accompanied by abrupt shifts in ocean circulation. However, the reason these deglacial abrupt events are so special compared with their sub-glacial-maximum analogues, in particular with respect to the exaggerated warming observed across Antarctica, remains unclear. Here we show that an increase in the relative importance of salt versus temperature stratification in the glacial deep South Atlantic decreases the potential cooling effect of waters that may be upwelled in response to abrupt perturbations in ocean circulation, as compared with sub-glacial-maximum conditions. Using a comprehensive coupled atmosphere–ocean general circulation model, we then demonstrate that an increase in deep-ocean salinity stratification stabilizes relatively warm waters in the glacial deep ocean, which amplifies the high southern latitude surface ocean temperature response to an abrupt weakening of the Atlantic meridional overturning circulation during deglaciation. The mechanism can produce a doubling in the net rate of warming across Antarctica on a multicentennial timescale when starting from full glacial conditions (as compared with interglacial or subglacial conditions) and therefore helps to explain the large magnitude and rapidity of glacial terminations during the late Quaternary.
| Original language | English |
|---|---|
| Pages (from-to) | 930–936 |
| Number of pages | 7 |
| Journal | Nature Geoscience |
| Volume | 14 |
| Issue number | 12 |
| DOIs | |
| Publication status | Published - 3 Dec 2021 |
Bibliographical note
Funding Information:We thank colleagues in the Paleoclimate Dynamics group at the Alfred Wegener Institute Helmholtz Center for Polar and Marine Research (AWI) in Bremerhaven for general support and the AWI Computing Centre for keeping the supercomputer running. M. Fahrenberg is acknowledged for downloading PMIP4 data, and we thank X. Shi for providing LGM salinity data for AWI-ESM. We acknowledge financial support by PACES and REKLIM through the Helmholtz association, as well as from PalMod (01LP1504A and 01LP1915A) through the German Federal Ministry of Education and Research to G.K. We also acknowledge financial support from the National Science Foundation of China (41988101 and 42075047) to X.Z. and UK NERC (grants NE/J008133/1 and NE/ L006405/1) to S.B. Development of PISM is supported by NSF grants PLR-1603799 and PLR-1644277 and NASA grant NNX17AG65G. Computational resources were made available by the infrastructure and support of the computing centre of the Alfred Wegener Institute in Bremerhaven and the DKRZ in Hamburg, Germany. The authors also thank all the modelling groups who provided the PMIP2, PMIP3 and PMIP4 output for analysis, WCRP, CMIP panel, PCMDI, ESGF infrastructures for sharing data, WCRP and CLIVAR for supporting the PMIP project. The Laboratoire des Sciences du Climat et de l’Environnement (LSCE) is acknowledged for collecting and archiving the PMIP2 model data. The PMIP2 Data Archive is supported by CEA, CNRS and the Programme National d’Etude de la Dynamique du Climat (PNEDC).
Publisher Copyright:
© 2021, The Author(s).