Date of Award

12-10-2025

Document Type

Thesis

Degree Name

Master of Science in Coastal Marine and Wetland Studies

Department

Coastal and Marine Systems Science

College

College of Science

First Advisor

April Abbott

Second Advisor

Angelos Hannides

Third Advisor

Zhixiong Shen

Additional Advisors

Stefan Lohr

Abstract

Individually and as a series, the Rare Earth Elements (REEs) are powerful geochemical tracers of environmental processes. However, ambiguities in the oceanic budgets of the REEs hamper their application. Growing evidence suggests a sedimentary benthic flux via the pore water is the major source of REEs to the ocean, with extrapolated estimates of this flux being equivalent in magnitude to that “missing” from modern budgets. However, existing pore water REE data are available from only a few locations globally with no representative dataset from the open North Atlantic. This data scarcity limits our ability to constrain flux estimates and understand their impacts in both the modern and past oceans. Here, I present pore water data from 8 sites representing the North Atlantic east coast margin, Labrador Sea, Irminger Sea, and Greenland Sea. I discuss the implications of these new data in terms of the mechanisms driving the benthic source fluxes, and in terms of the broader marine budget of REEs. My sites represent a range of water depths (1400 m to 4900 m), sediment compositions, grain size variations, and ice rafted debris (IRD) content. All sites sampled have elevated pore water REE concentrations relative to the overlying bottom water (Avg. BW 21 pM/L ± 6) indicating a sedimentary source to the marine budget, however our calculated flux from some sites was unexpectedly low. I suggest that this is either due to immediate uptake of the dissolved REE into solid authigenic phases, or that physical mixing and irrigation dominate pore fluid concentrations making diffusive calculations inappropriate. The greatest efflux was from sediments on the United States east continental margin fluxes (~6 pmol Nd cm-2yr-1), which are comparable to those observed in the slope sites of the North Pacific (Oregon Margin), and the lowest flux (~2 pmol cm-2 yr-1) at Station 04. The widespread occurrence of a benthic flux in the North Atlantic combined with the NADW flow path helps resolve the non-conservative observations of neodymium as the NADW passes through the Irminger Basin.

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