Paleoclimate changes in the Northwest Pacific Ocean as inferred from Mid-Pliocene Biogenic Silica at ODP Site 1207
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Issue Date
2024
Authors
Lembo-Ehms, Andrew
Publisher
SUNY Brockport: Friends of Drake Library
Keywords
Abstract
A sediment core containing biogenic opal was recovered from Ocean Drilling Program
(ODP) Site 1207, located on Shatsky Rise in the Northwest Pacific Ocean. Samples used in this
study span ~3.18-3.34 Ma and cover glacial-interglacial periods in the mid-Pliocene. The
assumption that the Oyashio and Kuroshio currents migrate north and south across ODP Site 1207
in response to Earth’s prevailing climate state will be tested. The Kuroshio Current is responsible
for transporting heat from the tropics towards higher latitudes in the northern hemisphere. The
mixed water region (MWR) bounded by the Oyashio and Kuroshio currents is nutrient-rich and
supports high biologic productivity. Biogenic silica (BSi) will be analyzed to understand
paleoproductivity of diatoms, an important phytoplankton. BSi, reported as %BSi, will be
extracted from sediments using a wet-alkaline digestion method and then measured as dissolved
silica (SiO2). %BSi at this site reflects productivity changes due to the migration of the nutrient
supplying ocean currents, as global climate changes through time. Results will be compared to
existing records from ODP Site 882 to assess how productivity responds to climate changes at a
mid-latitude site (1207) compared to high-latitude site (882). BSi productivity is a significant
pathway for carbon sequestration, with global climate implications. The mid-Pliocene section of
the sediment core provides an opportunity to study BSi productivity at a time when global
atmospheric carbon dioxide (CO2) concentrations were comparable to today. Low Bsi during a
period of warmer global temperatures might indicate a northward migration of the nutrient
supplying ocean currents. This is significant for understanding how present-day diatom
populations may respond to predicted climate changes, and successively, how Earth’s climate may
respond to the changes in diatom population size.
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