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The role of the Southern Ocean in abrupt transitions and hysteresis in glacial ocean circulation

Hines, Sophia K. V. and Thompson, Andrew F. and Adkins, Jess F. (2019) The role of the Southern Ocean in abrupt transitions and hysteresis in glacial ocean circulation. Paleoceanography and Paleoclimatology, 34 (4). pp. 490-510. ISSN 2572-4517. doi:10.1029/2018pa003415.

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High‐latitude Northern Hemisphere climate during the last glacial period was characterized by a series of abrupt climate changes, known as Dansgaard‐Oeschger (DO) events, which were recorded in Greenland ice cores as shifts in the oxygen isotopic composition of the ice. These shifts in inferred Northern Hemisphere high‐latitude temperature have been linked to changes in Atlantic meridional overturning strength. The response of ocean overturning circulation to forcing is non‐linear and a hierarchy of models have suggested that it may exist in multiple steady state configurations. Here, we use a time‐dependent coarse‐resolution isopycnal model with four density classes and two basins, linked by a Southern Ocean to explore overturning states and their stability to changes in external parameters. The model exhibits hysteresis in both the steady‐state stratification and overturning strength as a function of the magnitude of North Atlantic Deep Water (NADW) formation. Hysteresis occurs as a result of two non‐linearities in the model‐‐‐the surface buoyancy distribution in the Southern Ocean and the vertical diffusivity profile in the Atlantic and Indo‐Pacific basins. We construct a metric to assess circulation configuration in the model, motivated by observations from the Last Glacial Maximum, which show a different circulation structure from the modern. We find that circulation configuration is primarily determined by NADW density. The model results are used to suggest how ocean conditions may have influenced the pattern of DO events across the last glacial cycle.

Item Type:Article
Related URLs:
URLURL TypeDescription Itemmodel code
Hines, Sophia K. V.0000-0001-9357-6399
Thompson, Andrew F.0000-0003-0322-4811
Adkins, Jess F.0000-0002-3174-5190
Additional Information:© 2019 American Geophysical Union. Received 6 JUN 2018; Accepted 4MAR 2019; Accepted article online 15MAR 2019; Published online 5 APR 2019. We would like to thank Raffaele Ferrari, Emily Newsom, Andrew Stewart, David Marshall, James Rae, and Andrea Burke for helpful discussions, and two anonymous reviewers, whose comments improved the manuscript. S. K. V. H. received support from NSF grants OCE‐1503129 and OCE‐1204211 and the Lamont‐Doherty Earth Observatory Postdoctoral Fellowship. A. F. T. received support from the David and Lucille Packard Foundation and from NSF grant OCE‐1235488. J. F. A. received support from NSF grants OCE‐1503129, OCE‐1737404, and OCE‐1450528. The model code used for this paper will be available on GitHub at the website.
Funding AgencyGrant Number
Lamont–Doherty Earth Observatory (LDEO)UNSPECIFIED
David and Lucile Packard FoundationUNSPECIFIED
Subject Keywords:Abrupt climate change; Glacial ocean circulation; Ocean circulation; Hysteresis
Issue or Number:4
Record Number:CaltechAUTHORS:20190328-112956704
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Official Citation:Hines, S. K., Thompson, A. F., & Adkins, J. F. (2019). The role of the Southern Ocean in abrupt transitions and hysteresis in glacial ocean circulation. Paleoceanography and Paleoclimatology, 34, 490–510.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94246
Deposited By: George Porter
Deposited On:28 Mar 2019 22:15
Last Modified:16 Nov 2021 17:03

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