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Relatively warm deep-water formation persisted in the Last Glacial Maximum
Jack H Wharton1, Emilia Kozikowska2,3, Lloyd D Keigwin4
1Department of Geography, University College London, London, UK. jack.wharton.15@ucl.ac.uk.
Nature
|January 21, 2026
Summary
During the Last Glacial Maximum, the deep North Atlantic was only slightly colder than today. This research reveals sustained production of North Atlantic Deep Water, offering insights for climate models.
Area of Science:
- Paleoceanography
- Climate Science
- Oceanography
Background:
- The Last Glacial Maximum (LGM) featured colder global temperatures, extensive ice sheets, and altered atmospheric circulation.
- Understanding deep ocean conditions during the LGM is crucial for climate reconstructions but limited by data scarcity.
Purpose of the Study:
- To reconstruct the thermal and isotopic state of the deep Northwest Atlantic during the LGM.
- To investigate the origin and characteristics of deep water masses under glacial conditions.
Main Methods:
- Analysis of deep-sea sediment cores to obtain hydrographic data.
- Reconstruction of seawater temperature and isotopic composition (δ¹⁸O) for the glacial period.
Main Results:
- Glacial deep (>1.5 km) Northwest Atlantic temperatures were only 1.8 ± 0.5 °C colder than present.
- Seawater δ¹⁸O was 0.3 ± 0.1‰ higher, with origins traced to surface subtropics via the Northeast Atlantic and Nordic Seas.
- Evidence suggests sustained production of relatively warm and saline North Atlantic Deep Water during the LGM.
Conclusions:
- The deep Northwest Atlantic maintained a distinct thermal and isotopic structure during the LGM.
- Findings challenge previous assumptions about deep ocean circulation and properties under glacial forcing.
- Results provide critical data for validating and improving Earth system models for future climate projections.
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