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Provedor de dados:  ArchiMer
País:  France
Título:  Abrupt climate variability during the last glacial and the late Holocene from the western tropical Pacific perspective
Autores:  Saikku, Reetta Maaria
Data:  2009
Ano:  2009
Palavras-chave:  Climate
Resumo:  In Project I, Western tropical Pacific sea surface temperatures and Pacific Deep Water temperatures during Marine Isotope Stage 3 have been reconstructed from the δ18O and Mg/Ca of planktonic and benthic foraminifera from Marion Dufresne core MD98-2181. This 36m marine core was collected at 6.3°N from a water depth of 2114m. With sediment accumulation rates of up to 80cm/ky, it provides a decadally-resolved history of ocean variability during the last glacial period. Surface temperatures and salinities at this site varied in close association with millennial-scale atmospheric temperature swings at high northern latitudes as reflected in the GISP2 ice core. At times of colder atmospheric temperatures over Greenland, the western Pacific was more saline and summer season SSTs were ~2oC colder. These millennial scale changes within the tropics are attributed to a southward displacement of the summer season ITCZ in response to steeper meridional temperature gradients within the Pacific. The benthic δ18O record from MD98-2181 documents upper Pacific Deep Water temperature and salinity variability. Benthic δ18O variations of 0.3-0.5‰ during MIS 3 indicate deep waters within the Pacific were varying by ~1-1.5°C, with the possibility that some of the variability was due to changing salinity and minor glacial-eustatic changes.; The observed deep water variability correlates to changes in Antarctic surface temperatures and thus reflects changes in Southern Ocean temperatures at the site of Pacific Deep Water formation. The combined planktonic and benthic records from MD98-2181 thus provides a northern and southern hemispheric climate record of anti-phased variability during MIS 3 as has been inferred previously from ice core records. Furthermore, the deep sea temperature excursions appear to have led millennial variations in atmospheric CO2 as recorded in the EDML ice core by ~1kyr. It is therefore hypothesized that the CO2 may have been outgassed from a less stratified Southern Ocean.; Project II presents a 2000-year record of Mg/Ca and δ18O measurements on planktonic, and δ18O measurements on benthic foraminifera from continuous marine cores taken from high sedimentation sites in the Western Pacific Warm Pool. The western Pacific warm pool exhibits decadal- to centennial-scale variability. The Little Ice Age is recorded as the coldest and Medieval Warm Period as the warmest over last 2ka (data does not include the last 150yrBP). The MD81 benthic record suggests a large drop in temperature of ~1°C, which may also include a salinity component. This event correlates with other proxy records from the Southern Ocean confirming the event as Southern Hemisphere-wide. Due to the ideal core location of MD81 it was also possible to address the question of phasing of the northern and southern climate records and whether the "bipolar seesaw" was still active during the Holocene. The 2000-year surface record from the western Pacific warm pool exhibits centennial scale variability, with larger, potentially millennial-scale oscillations present within the last 1000 years, as recorded by two marine sediment cores. However, based on the available data there is no evidence for a bipolar seesaw during the large benthic cooling event.
Tipo:  Text
Idioma:  Inglês
Editor:  University of Southern California
Formato:  application/pdf
Direitos:  info:eu-repo/semantics/openAccess

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