A dynamical reconstruction of the Last Glacial Maximum ocean state constrained by global oxygen isotope data.

Breitkreuz, Charlotte , Paul, André and Schulz, Michael (Submitted) A dynamical reconstruction of the Last Glacial Maximum ocean state constrained by global oxygen isotope data. Open Access Climate of the Past . pp. 1-24. DOI 10.5194/cp-2019-52.

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Combining ocean general circulation models with proxy data via data assimilation is a means to obtain estimates of past ocean states that are consistent with model physics as well as with proxy data. The climate during the Last Glacial Maximum (LGM, 19–23 ka) was substantially different from today. Even though boundary conditions are comparatively well known, the large-scale patterns of the ocean circulation during this time remain uncertain. Previous efforts to combine ocean models with proxy data have shown dissimilar results regarding the state of the ocean, in particular of the Atlantic Meridional Overturning Circulation. Here, we present a new LGM ocean state estimate that extents previous estimates by using global benthic as well as planktic data on the oxygen isotopic composition of calcite. It is further constrained by global seasonal and annual sea surface temperature (SST) reconstructions. The estimate shows an Atlantic Ocean that is similar to the Late Holocene Atlantic Ocean but with a reduced formation of Antarctic Bottom Water, in contrast to results of previous studies. The results indicate that SST and oxygen isotopic data alone do not require the presence of a shallower North Atlantic Deep Water and a more extensive Antarctic Bottom Water, and highlight the need for more proxy data of different types to obtain reliable ocean state estimates. Additional adjoint sensitivity experiments reveal that data from the deep North Atlantic and from the global deep Southern Ocean are most important to constrain the Atlantic Meridional Overturning Circulation.

Document Type: Article
Additional Information: This preprint was under review for the journal CP. A revision for further review has not been submitted.
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.5194/cp-2019-52
ISSN: 1814-9332
Projects: PalMod
Date Deposited: 13 May 2020 08:15
Last Modified: 13 May 2020 08:15
URI: http://oceanrep.geomar.de/id/eprint/49656

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