Late Eocene onset of the Proto-Antarctic Circumpolar Current

Abstract

The formation of the Antarctic Circumpolar Current (ACC) is critical for the evolution of the global climate, but the timing of its onset is not well constrained. Here, we present new seismic evidence of widespread Late Eocene to Oligocene marine diagenetic chert in sedimentary drift deposits east of New Zealand indicating prolonged periods of blooms of siliceous microorganisms starting ~36 million years ago (Ma). These major blooms reflect the initiation of the arrival and upwelling of northern-sourced, nutrient-rich deep equatorial Pacific waters at the high latitudes of the South Pacific. We show that this change in circulation was linked to the initiation of a proto-ACC, which occurred ~6 Ma earlier than the currently estimated onset of the ACC at 30 Ma. We propose that the associated increased primary productivity and carbon burial facilitated atmospheric carbon dioxide reduction contributing to the expansion of Antarctic Ice Sheet at the Eocene-Oligocene Transition.

Evolution and biogeography of actinorhizal plants and legumes: A comparison

“…Representative species of the nitrogen-fixing root nodule (NFN) clade and an adaptive feature, the cluster root, found in some members of the NFN clade that are adapted to low levels of soil phosphorus. have contributed to global cooling and the glaciation of Antarctica during the Late Eocene (Sarkar et al, 2019). The mostly submerged continent of Zealandia (including present day New Zealand and New Caledonia) had separated earlier from Antarctica, c. 80…”

“…Although Schrire and colleagues have hypothesised that the Leguminosae originated during the Palaeocene in dry biomes north of the Tethys Sea (Schrire et al, 2005), recent research infers that the Detarioideae had a post-Gondwanan origin 68-64 Mya (de la Estrella et al, 2017). The mass extinction event at the K-Pg boundary is associated with the rapid diversification of Leguminosae lineages in the Tertiary period, together with multiple nested polyploidy events, which are thought to have underpinned the evolutionary success of the Leguminosae in the Cenozoic Lavin et al, 2005;LPWG, 2017 (Sarkar et al, 2019). The mostly submerged continent of Zealandia (including present day New Zealand and New Caledonia) had separated earlier from Antarctica, c. 80…”

Fifty million years of beetle evolution along the Antarctic Polar Front

“…25), a dynamic geo-climatic history (6,26), a profound degree of isolation, and indications that climatic events likely structured their biota (6,8,27). The terrestrial habitat on the continent and its surrounding islands is fragmented by large expanses of ice or ocean, respectively, and has been further isolated by the Antarctic Circumpolar Current for at least 34 Ma (28,29). Cyclic growth and contraction of ice sheets throughout the Plio-Pleistocene, though typically associated with the continent, has also had extensive impacts on the sub-Antarctic islands (26).…”

Genetic diversity of soil invertebrates corroborates timing estimates for past collapses of the West Antarctic Ice Sheet

“…1 ). Many taxa in these ice-free areas have presumably survived repeated glacial cycles in local refugia, with some taxa dating back to before isolation of the Antarctic continent and establishment of the Antarctic Circumpolar Current ∼34 Mya to 36 Mya ( 6 , 7 ). The distribution of many Antarctic soil taxa such as lichens, nematodes, and microarthropods is disjunct ( 8 – 10 ) and does not conform to conventional patterns of diversity which usually show decreasing trends with increasing latitude (i.e., the Latitudinal Diversity Gradient; ref.…”