Publication Date

2024

Document Type

Dissertation/Thesis

First Advisor

Scherer, Reed P.

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Earth, Atmosphere, and Environment (EAE)

Abstract

Located off the coast of the West Antarctic Ice Sheet, the Scotia Sea is a site of great significance in palaeoclimatological studies due to the nature of its sedimentary record. This site of interest is at the tip of the Antarctic Peninsula on the Eastern side, in the direct flow of the Antarctic Circumpolar Current thereby concentrating icebergs from around the continent. Additionally, these sediments are rich in diatoms. Finally, this site, within the analyzed section, has an average sedimentation rate of ~48 cm/Kyr.

By collecting sediment cores rich in diatoms, among material used to generate other paleoclimate proxies, we can gain insight into the variability of environmental and climatic conditions and interactions over time. Diatoms are primary producers which respond rapidly to environmental change and are made up of two siliceous valves that make up a frustule that readily preserve in sediments, making them a useful tool in climate studies. Sediment samples were taken from the composite splice retrieved from IODP Site U1537 at a resolution of one sample per 20 cm. This study uses samples that cover the last ~30,000 years and analyzed Absolute Diatom Abundance (ADA) and Relative Diatom Abundance (%A), i.e., percent species relative abundance, associated diatoms groups with known ecological affiliations.

Four ecological groups are primarily found at this site, the Well Mixed, Open Ocean, Sea Ice, and Subtropical groups. Results, covering the previous ~30 ka, present an inverse correlation of the Absolute Diatom Abundance with the LR04 benthic oxygen isotope stack, with diatoms increasing in abundance from the glacial to the Holocene. This occurs in conjunction with a decrease in abundance of the Sea Ice group of diatoms, implying increased overall productivity in warmer water. This follows what has been seen previously in the Southern Ocean. Warmer water over the site created a preferred environment for the Open Ocean and Subtropical groups of diatoms following the deglacial. However, this site has recorded a warm Southern Ocean signature through the studied interval, as the Open Ocean group of diatoms maintain a steady abundance (60-70%) despite changes in ADA. This relationship suggests that at this site the primary driver of abundance variability is not the temperature, but more likely tied to the nutrient availability. This hypothesis is supported by changes to the relative abundance of two Open Ocean group diatoms: Fragilariopsis kerguelensis which thrives in nutrient rich environments and Thalassiosira lentiginosa which can succeed in low nutrient conditions. The ultimate driver of these changes is likely the passage of the Antarctic Circumpolar Current over the site to a more southerly position through the deglacial.

Understanding the drivers of the temperature/productivity relationship, as well as species data from this site, can help us understand more about the variation of the climatic and ecological setting of the West Antarctic Ice Sheet and the Scotia Sea in specific and the variation in the location of the polar front over time. This study will increase the amount of data that we have both in location and depth at this site, increasing our knowledge of the West Antarctic Ice Sheet history and its impact on Southern Ocean primary productivity.

Extent

61 pages

Language

en

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

Download

Included in

Climate Commons

Share

COinS