Impact of the Agulhas Return Current on the oceanography of the Kerguelen Plateau region, Southern Ocean, over the last 40 kyrs

Antarctic Polar Front migrations in the Kerguelen Plateau region, Southern Ocean, over the past 360 kyrs

“…As previously observed in a 40 kyrs long record recovered east of KI (Civel-Mazens et al, 2021), the sub-STrad pattern in core MD11-3353 on a depth scale is exceptionally similar to the EDC ice core δD record (Thöle et al, 2019). Our new record extends this finding by three climate cycles (Figure 2).…”

“…Downstream of the KP, the surface waters at the MD12-3396CQ core site (47°43'S and 86°41'E, east of KI) were influenced by lower latitudes warmth redistributed via the Agulhas Return Current (RC) to the SIO during the MIS 2 -3(Civel-Mazens et al, 2021). Contrary to the SSTdiat, sub-STrad in this core did not record the injection of low latitude warmth, which was limited to the surface layer of the ocean, and sub-STrad can, therefore, reliably trace the θ min 2 °C.…”

Ecoregionalisation of the Southern Ocean Using Radiolarians

“…Assemblage distribution is also known to be strongly related to temperature (Boltovskoy and Correa, 2016). Methods for reconstructing sea surface temperatures (SST) were developed which applied factor analysis and transfer functions for paleotemperature estimates throughout the SO (Imbrie and Kipp, 1971;CLIMAP, 1976CLIMAP, , 1981Cortese et al, 2013;Panitz et al, 2015;Prebble et al, 2017;Civel-Mazens et al, 2021b). Radiolarians have also been used as indicators for upwelling in some tropical regions, where characteristic assemblages have been utilized to understand past upwelling processes.…”

“…Radiolarian assemblages of the SO-RAD surface sediment census dataset (Lawler et al, 2021) were found to be heterogeneous both latitudinally and longitudinally. We expected the assemblages to vary latitudinally due to strong associations between radiolarian assemblages and sea surface and sub-surface temperature, one of the main reasons why radiolarians have typically been used as temperature proxies (Abelmann et al, 1999;Cortese and Abelmann, 2002;Panitz et al, 2015;Civel-Mazens et al, 2021b). However, if temperature were the only driver of radiolarian distribution, we would expect to see homogeneity of assemblage composition along isotherms, which are characteristically longitudinal throughout the SO.…”

“…Therefore, radiolarians do not appear to respond to a single variable, but rather a combination. Previous work using radiolarians as a proxy for temperature appear robust (Cortese et al, 2013;Panitz et al, 2015;Prebble et al, 2017;Civel-Mazens et al, 2021b) suggesting that temperature has a strong influence on the distribution of radiolarians (Boltovskoy and Correa, 2016;Hernández-Almeida et al, 2017). Furthermore, the use of radiolarian indices for oceanographic features such as upwelling and water masses have also shown potential, for example the Upwelling Radiolarian Index and Water Depth Ecology index (Lazarus et al, 2006;Nigrini and Caulet, 1992).…”