Glacial-interglacial changes in sea surface temperature of the North Pacific subtropical gyre /
A knowledge of sea surface temperatures (SSTs) in the subtropical Pacific during the last glaciation is important because the variations of SSTs in low to subtropical latitudes are strongly related with climatic changes. Yet, previous attempts to estimate glacial SSTs in the subtropical North Pacifi...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1999.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=733674221&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | A knowledge of sea surface temperatures (SSTs) in the subtropical Pacific during the last glaciation is important because the variations of SSTs in low to subtropical latitudes are strongly related with climatic changes. Yet, previous attempts to estimate glacial SSTs in the subtropical North Pacific from the marine sedimentary records have been hindered by the scarcity of cores with well preserved carbonate microfossils. To investigate glacial-interglacial SST variations in this region, we used two shallow water piston cores with relatively high deposition rate, recovered from near Oahu, Hawaii. Shallow water depth and high sedimentation rate minimize the effects of dissolution and bifurcation. SSTs were estimated based upon four independently measured parameters: 1) oxygen isotope ratios of the planktonic foraminifera Globigerinoides Tuber, 2) assemblages of planktonic foraminifera characterized using the Modern Analog Technique (MAT), 3) the U[] of alkenones in bulk sediment, and 4) Mg/Ca ratios of planktonic foraminifera Globigerinoides sacculifer. The two cores yield similar SST records, and the three different approaches ([], foraminiferal assemblages, and U[]) produced consistent results of SSTs estimates.[]O-based temperature estimates reflecting summer SST indicate that the change in glacial/interglacial SSTs is more than 1C̊, which is comparable to the results of MAT August estimates ([]T[] = ~1C̊). U[]-based temperature estimates indicate that winter SSTs near Hawaii were about 3C̊ colder during the last glacial maximum (LGM) than today, which is consistent with the results of MAT February estimates ([]T[] = ~3C̊). Paleotemperature estimates from Mg/Ca ratios of Globigerinoides sacculifer indicate that glacial SSTs were about 1-2C̊ colder than today. However, the SST estimates based on Mg/Ca ratio were limited by several factors such as gametogenic calcite, postdepositional alteration, and contamination. These results indicate that glacial average annual SSTs in the subtropical North Pacific are about 2C̊ colder than today, and 4C̊ colder than estimated by CLIMAP (1981). These results have important implications for the evaluation of the sensitivity of climate models, for our understanding the subtropical Pacific's influence on global climate (e.g., its effects on extratropical Northern Hemisphere climate and ocean heat transport), and may help explain glacial scowling depressions on Hawaii. |
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| Item Description: | Vita. "Major Subject: Oceanography". |
| Physical Description: | xi, 92 leaves : illustrations and maps ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 57-65). |