Revisiting the geographical extent of exceptional warmth in the Early
Paleogene Southern Ocean
Abstract
To assess zonal temperature and biogeographical patterns in the
Paleogene of the Southern Ocean, 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 proxies document the
well-known late Paleocene gradual warming and, superimposed, two late
Paleocene pre-cursor warming events, hundreds of kyrs prior to the PETM.
Remarkably, however, air and sea surface temperature reconstructions for
the AAG and SW Pacific during the latest Paleocene, PETM and Early
Eocene Climatic Optimum (~53–49 Ma) show similar trends
and, within proxies, similar absolute temperatures. The record implies
that the exceptional warmth previously recorded in the SW Pacific
extended westward into the AAG. This contrasts with the modeled
circulation and temperature patterns. We suggest that simulations of
ocean circulation underestimate heat transport in the SW Pacific due
insufficient resolution, not allowing for mesoscale eddy-related heat
transport. We argue for a systematic approach to tackle model and proxy
biases in marginal marine settings, including assessment of
underexplored factors as high-latitude proxy mechanisms to confidently
assess temperature in these non-analogue climates.