Revisiting the Geographical Extent of Exceptional Warmth in the Early Paleogene Southern Ocean. Issue 3 (4th March 2023)

• Record Type: Journal Article
• Authors: Frieling, J.; Bohaty, S. M.; Cramwinckel, M. J.; Gallagher, S. J.; Holdgate, G. R.; Reichgelt, T.; Peterse, F.; Pross, J.; Sluijs, A.; Bijl, P. K.
• Is Part Of: Paleoceanography and paleoclimatology. Volume 38:Issue 3(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-03-04
• Subjects: Paleocene‐Eocene Thermal Maximum -- temperature reconstruction -- multi‐proxy -- paleoceanography -- SW Pacific -- Australo‐Antarctic Gulf; Paleoceanography -- Periodicals; Paleoclimatology -- Periodicals; 551.46
• DOI: 10.1029/2022PA004529
• Languages: English
• ISSNs: 2572-4517

Abstract

Abstract: To assess zonal temperature and biogeographical patterns in the Southern Ocean during the Paleogene, we present new multi‐proxy air‐ and sea‐surface temperature data for the latest Paleocene (∼57–56 Ma) and the Paleocene‐Eocene Thermal Maximum (PETM; ∼56 Ma) from the northern margin of the Australo‐Antarctic Gulf (AAG). The various proxy data sets document the well‐known late Paleocene warming and, superimposed, two transient late Paleocene pre‐cursor warming events, hundreds of kyr prior to the PETM. Remarkably, temperature reconstructions for the AAG and southwest Pacific during the latest Paleocene, PETM and Early Eocene Climatic Optimum (∼53–49 Ma) show similar trends as well as similar absolute temperatures east and west of the closed Tasmanian Gateway. Our data imply that the exceptional warmth as recorded by previous studies for the southwest Pacific extended westward into the AAG. This contrasts with modeling‐derived circulation and temperature patterns. We suggest that simulations of ocean circulation underestimate heat transport in the southwest Pacific due to insufficient resolution, not allowing for mesoscale eddy‐related heat transport. We argue for a systematic approach to tackle model and proxy biases that may occur in marginal marine settings and non‐analog high‐latitude climates to assess the temperature reconstructions. Plain Language Summary: For the Cenozoic (past 66 million years) there is a good correspondence between climate conditions derived from numerical models and those from reconstructions on sediment cores, but in some regions fundamental discrepancies between the two require further understanding. We test the extent and potential origin of a remaining discrepancy: the Paleocene‐Eocene southwest Pacific. In this region proxy‐based sea surface temperature reconstructions are much warmer than modeled. Our new temperature reconstructions from the Australo‐Antarctic Gulf are strikingly similar to those from the southwest Pacific, while the closed Tasmanian Gateway separates these two basins into fundamentally different oceanographic settings. The overall pattern might be attributed to systematic underestimation of high‐latitude warm‐current invasion in low‐resolution climate models. A better understanding of temperature proxies in non‐analog climates is likely also required to validate the exceptional high‐latitude warmth recorded in our data. Key Points: Temperature reconstructions for the late Paleocene and Paleocene‐Eocene Thermal Maximum show identical temperature in the Australo‐Antarctic Gulf and the SW Pacific The zonally identical temperatures contrast with climate model runs and projected ocean currents The relatively low spatial resolution of current climate models may underestimate heat transport from meso‐scale eddies to the SW Pacific