Highly variable Pliocene sea surface conditions in the Norwegian Sea

Bachem, Paul E.; Risebrobakken, Bjørg; De Schepper, Stijn; McClymont, Erin L.

Abstract

The Pliocene was a time of global warmth with small sporadic glaciations, which transitioned towards the larger-scale Pleistocene glacial–interglacial variability. Here, we present high-resolution records of sea surface temperature (SST) and ice-rafted debris (IRD) in the Norwegian Sea from 5.32 to 3.14 Ma, providing evidence that the Pliocene surface conditions of the Norwegian Sea underwent a series of transitions in response to orbital forcing and gateway changes. Average SSTs are 2 °C above the regional Holocene mean, with notable variability on millennial to orbital timescales. Both gradual changes and threshold effects are proposed for the progression of regional climate towards the Late Pliocene intensification of Northern Hemisphere glaciation. Cooling from 4.5 to 4.3 Ma may be linked to the onset of poleward flow through the Bering Strait. This cooling was further intensified by a period of cool summers due to weak obliquity forcing. A 7 °C warming of the Norwegian Sea at 4.0 Ma suggests a major increase in northward heat transport from the North Atlantic, leading to an enhanced zonal SST gradient in the Nordic Seas, which may be linked to the expansion of sea ice in the Arctic and Nordic Seas. A warm Norwegian Sea and enhanced zonal temperature gradient between 4.0 and 3.6 Ma may have been a priming factor for increased glaciation around the Nordic Seas due to enhanced evaporation and precipitation at high northern latitudes.

Citation

Bachem, P. E., Risebrobakken, B., De Schepper, S., & McClymont, E. L. (2017). Highly variable Pliocene sea surface conditions in the Norwegian Sea. Climate of the Past, 13(9), 1153-1168. https://doi.org/10.5194/cp-13-1153-2017

• Journal Article Type: Article
• Acceptance Date: Jul 10, 2017
• Online Publication Date: Sep 11, 2017
• Publication Date: Sep 11, 2017
• Deposit Date: Sep 15, 2017
• Publicly Available Date: Sep 18, 2017
• Journal: Climate of the Past
• Print ISSN: 1814-9324
• Electronic ISSN: 1814-9332
• Publisher: European Geosciences Union
• Peer Reviewed: Peer Reviewed
• Volume: 13
• Issue: 9
• Pages: 1153-1168
• DOI: https://doi.org/10.5194/cp-13-1153-2017
• Public URL: https://durham-repository.worktribe.com/output/1344904