Coccolithophore estimates of paleotemperature and paleoproductivity changes in the southeast Pacific over the past ∼27 kyr

Abstract

We provide high‐resolution sea surface temperature (SST) and paleoproductivity data focusing on Termination 1. We describe a new method for estimating SSTs based on multivariate statistical analyses performed on modern coccolithophore census data, and we present the first downcore reconstructions derived from coccolithophore assemblages at Ocean Drilling Project (ODP) Site 1233 located offshore Chile. We compare our coccolithophore SST record to alkenone‐based SSTs as well as SST reconstructions based on dinoflagellates and radiolaria. All reconstructions generally show a remarkable concordance. As in the alkenone SST record, the Last Glacial Maximum (LGM, 19–23 kyr B.P.) is not clearly defined in our SST reconstruction. After the onset of deglaciation, three major warming steps are recorded: from 18.6 to 18 kyr B.P. (∼2.6°C), from 15.7 to 15.3 kyr B.P. (∼2.5°C), and from 13 to 11.4 kyr B.P. (∼3.4°C). Consistent with the other records from Site 1233 and Antarctic ice core records, we observed a clear Holocene Climatic Optimum (HCO) from ∼8–12 kyr B.P. Combining the SST reconstruction with coccolith absolute abundances and accumulation rates, we show that colder temperatures during the LGM are linked to higher coccolithophore productivity offshore Chile and warmer SSTs during the HCO to lower coccolithophore productivity, with indications of weak coastal upwelling. We interpret our data in terms of latitudinal displacements of the Southern Westerlies and the northern margin of the Antarctic Circumpolar Current system over the deglaciation and the Holocene.

Cocolitoforos en sedimentos marinos frente a la entrada occidental del Estrecho de Magallanes (53S) revelan cam-bios en la productividad durante los ultimos 30.000 anos

“…In general, both records were in phase with alkenone-derived sea-surface temperature (Caniupán et al, 2011) where maximum values of CaCO3 (>30%) and coccolith abundance (~10 9 coccoliths g -1 dry sediment) coincided with relatively warm periods (e.g., the Holocene). We found marked differences when comparing our data with a coccolith record published by Saavedra-Pellitero et al (2011) for ODP Site 1233 at 41°S: At ODP Site 1233, coccolithophore production was maximal during the Last Glacial Maximum in response to the northward advection of macronutrients by the Antarctic Circumpolar Current. In contrast, site MD07-3128 experienced a reduction in coccolithophore production at the time, probably related to the negative effect exerted by the high inputs of terrigenous material and meltwater from the then nearby located large Patagonian Ice Sheet.…”

“…Combinando la información de datos de abundancia y distribución de cocolitos y condiciones oceanográficas de la zona, Saavedra-Pellitero et al (2010) determinaron, mediante un análisis multivariado, tres factores que asocian las masas de agua y especies de cocolitóforos características de las mismas. Adicionalmente, Saavedra-Pellitero et al (2011) vincularon las temperaturas más frías del Último Máximo Glacial (UMG) con una mayor productividad de cocolitóforos en el margen continental chileno a 41°S, que estaría asociado a un incremento en la advección de macronutrientes dado el desplazamiento de 5-6° de latitud hacia el norte de los Vientos del Oeste y de la Corriente Circumpolar Antártica (CCA). En contraste, las TSM más cálidas registradas durante el Holoceno temprano se asociaron a una menor productividad de cocolitóforos sugiriendo un desplazamiento hacia el sur del sistema oceánico/atmosférico.…”

“…1a-1b), concentrándose en los últimos ~30.000 años AP. Estos datos se combinan con los datos de paleo-temperaturas del mismo testigo (Caniupán et al, 2011) y se comparan con los publicados por Saavedra-Pellitero et al (2011) a los 41°S (Sitio ODP 1233), entregando así información nueva y relevante para el conocimiento de este grupo de nanoplancton en la región.…”

Modern sea surface productivity and temperature estimations off Chile as detected by coccolith accumulation rates

“…371 8A). Nevertheless, even if the three reconstructions follow the same trend, our SST 372 estimates are always lower than the other two because we considered an annual SST due to the fact that coccolithophore production can also happen at deeper depths (e.g., F. 380 profunda); this choice also allowed us directly to compare with the SST estimates based 381 on coccolith percentages (Saavedra-Pellitero et al, 2011). Both reconstructions based on 382 coccolithophores follow the same trend as the SST observed, although the SST CAR 383 estimates fits better (see Fig.…”

“…360 Abrantes et al (2007) added some samples to previously collected databases (e.g., 361 Schuette and Schrader, 1979;Romero and Hebbeln, 2003) and successfully obtained a 362 SST diatom transfer function based directly on species percentages. Many of those 363 samples were also used by Saavedra-Pellitero et al (2011) to estimate SST using 364 multivariate statistical analyses performed on modern coccolithophore census data from 365 15°N to 50.6°S and from 71°W to 93°W. With our work we covered an existing gap in 366 the north-central Chilean coast (from ~23ºS to ~33ºS) due to the lack of preserved 367 diatoms in the samples (Fig.…”