Researcher ORCID Identifier


Graduation Year


Document Type

Open Access Senior Thesis

Degree Name

Bachelor of Arts


Environmental Analysis

Reader 1

Dr. Branwen Williams

Reader 2

Dr. Jerry F. McManus

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© 2021 Ava C McIlvaine


The repeated occurrence of episodic iceberg-discharge events and abrupt climate change in the North Atlantic Ocean is well-documented for the late Quaternary period. However, much of the evidence for these periods known as Heinrich Events comes from the subpolar region, where deposition can be dominated by ice-rafted debris (IRD) and overwhelm other oceanographic and climatic indicators. Thus, the following analysis of coarse sediment from Integrated Ocean Drilling Program (IODP) Core Site U1313 (41°0.0'N, 32°57.42'W) evaluated ocean cooling related to ice-rafting, water mass migration, and climate change over the approximate last 100,000 years. Site U1313 is located near the North Atlantic Ocean’s subpolar-subtropical gyre boundary and has the potential to enhance the existing record of Heinrich events both temporally and spatially. IODP Site U1313 (reoccupation of Deep Sea Drilling Project (DSDP) Site 607) is situated on the western flank of the Mid-Atlantic Ridge (3413 m) at a climatically sensitive location that is currently bathed at depth by North Atlantic Deep Water (NADW). Investigation into the core’s coarse sediment (>150 µm fraction) documented the presence of polar planktonic foraminifera species N. pachyderma (sinistral), subpolar species T. quinqueloba, transitional species G. inflata, and IRD, indicating the possible past extension and retraction of colder poleward waters into the temperate central North Atlantic Ocean. The addition of Site U1313’s reconstructed regional signal into the complex history of the North Atlantic contributes to our current understanding of the strength, timing, and spatial extent of past iceberg-discharge events. Site U1313 shows that Heinrich Events repeatedly influenced the central North Atlantic Ocean and were associated with nuances in the region’s surface ocean conditions. This study’s high-resolution record draws our attention back to the influence of changing Sea Surface Temperatures (SSTs) on the biogeochemical composition of the water column. Core U1313 expands upon existing research into the impacts of climate variability in the North Atlantic by providing new insight from the subtropical-subpolar transitional zone into the role of the cryosphere and surface ocean circulation during periods of abrupt climate change in the last glaciation.

Ava C. McIlvaine Thesis Appendix .pdf (1954 kB)
Supplementary Material