Radium isotopes as tracers of boundary inputs of nutrients and trace elements to the coastal and open ocean
Citable URI
https://hdl.handle.net/1912/10646DOI
10.1575/1912/10646Keyword
Radium; Marine sciencesAbstract
Nutrients and trace metals are vital for supporting life in the ocean, but the boundary processes
that control the distributions of these elements are poorly constrained. Radium isotopes are well
suited to studying inputs of elements from ocean margins because they are produced in
sediments and soluble in seawater. The half-lives of the four isotopes (223Ra, 224Ra, 228Ra, 226Ra)
range from days to thousands of years, thus these isotopes can be used to study oceanographic
processes occurring over a range of time scales. In this thesis I have applied the quartet of radium
isotopes to investigate boundary inputs, including seafloor hydrothermal vents, continental
shelves, and rivers.
First, radium isotope ratios were used to constrain the age of hydrothermal plumes emanating
from vents along the Mid-Atlantic Ridge and East Pacific Rise. These radium-derived ages were
applied to determine the iron residence time in the Pacific plume that emanates from near 15°S,
providing an important constraint on the hydrothermal delivery of iron to the deep ocean. Next,
228Ra was used to show that shelf inputs to the Arctic Ocean have increased over the last decade,
implying that the fluxes of other shelf-derived materials are also increasing and could impact
primary production in this basin. The ratio of 228Ra and 226Ra was also applied to determine the
ventilation time of Arctic intermediate waters with respect to shelf inputs, and the first
measurements of 226Ra in the deep Canada Basin were used to estimate the residence time of
deep waters with respect to benthic sediment inputs. Finally, a study of the Mackenzie River
Estuary illustrated the importance of deltaic and estuarine processing on the ultimate delivery of
nutrients, trace metals, dissolved organic matter, and radium to the Arctic Ocean. By applying
radium isotopes as tracers of boundary inputs in these diverse environments, the work presented
in this thesis improves our understanding of nutrient and trace metal inputs to the coastal and
open ocean.
Description
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy
at the
Massachusetts Institute of Technology
and the
Woods Hole Oceanographic Institution
September 2018
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Suggested Citation
Thesis: Kipp, Lauren, "Radium isotopes as tracers of boundary inputs of nutrients and trace elements to the coastal and open ocean", 2018-09, DOI:10.1575/1912/10646, https://hdl.handle.net/1912/10646Related items
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