Climate-ice sheet-ocean interactions in the Gulf of Alaska through the Pliocene and Pleistocene
Global climate is characterised by a long term cooling trend since the Pliocene. However, we lack climate records from the North Pacific to confirm this. The proximity of the GOA to the Mount St. Elias, the highest mountain in the world uplifted during the Plio-Pleistocene, makes the location a targ...
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| Format: | Thesis |
| Language: | unknown |
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2018
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| Online Access: | http://etheses.dur.ac.uk/12634/ http://etheses.dur.ac.uk/12634/1/Maria_Luisa_Sa%CC%81nchez_Montes-E-Thesis.pdf |
| Summary: | Global climate is characterised by a long term cooling trend since the Pliocene. However, we lack climate records from the North Pacific to confirm this. The proximity of the GOA to the Mount St. Elias, the highest mountain in the world uplifted during the Plio-Pleistocene, makes the location a target to study the Pacific climate evolution towards present climate, the influence over the growth of large ice sheets over North America as well as the tectonic-ice sheet-climate interactions. This is important as the mid-Pliocene and MIS 5e have been identified as potential analogues for current climate. This thesis focuses on the Pliocene and Pleistocene study of Site U1417 (~700km away from the coast) and U1418 (~150km away from the coast) from the Gulf of Alaska, recovered during IODP Expedition 341. Biomarker extraction and analyses are used for sea surface temperature (SSTs from UK37 and UK37’ indices), sea surface salinity (C37:4), terrestrial and aquatic organic carbon inputs (long, short chain n-alkanes, TAR index, TOC, TON, δ13C and δ15N), marine productivity (alkenone, β-sitosterol, brassicasterol, dinosterol, TOC, TON, δ13C and δ15N concentrations) reconstructions at both sites. We conclude that SST during the early Pleistocene in the GOA was an average of 1°C warmer than during the late Pliocene, the last 500kyr and at modern. The Cordilleran Ice-Sheet developed since 2.8 Ma due to St. Elias tectonic uplift. The Cordilleran Ice-Sheet growth is fed by the humidity of a relatively warm and stratified surface ocean and orographic precipitation since the Pliocene. During the last 500 kyr, warmer SST intervals are associated with a decrease in ocean stratification. Nutrient availability in the GOA is the main control for coccolithophore productivity export reduction since the early Pleistocene. Modern ocean circulation across the North Pacific was established during the LGM and possibly since MIS 4. |
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