Publication Date:
2022-05-25
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 June 2013
Description:
This thesis explores the role that the circulation in the Gulf of Maine (GOM) plays
in determining the distribution of dense aggregations of copepods. These aggregations
are an important part of the marine ecosystem, especially for endangered North
Atlantic right whales. Certain ocean processes may generate dense copepod aggregations,
while others may destroy them; this thesis looks at how different characteristics
of the GOM circulation fit into these two categories.
The first part of the thesis investigates a hypothetical aggregation mechanism in
which frontal circulation interacts with copepod behavior to generate a dense patch of
copepods. The first two chapters of this thesis address this mechanism in the context
of coastal river plumes and salinity fronts. One chapter describes the characteristics
and variability of coastal freshwater and salinity fronts using a historical dataset
and a realistic numerical model. The seasonal variability of freshwater is tied in
part to seasonality in river discharge, while variability on shorter time scales in the
frontal position is related to wind stress. Another chapter applies the hypothetical
mechanism to idealized river plumes using a suite of numerical models. The structure
of the plume and plume-relative circulation change the resulting copepod aggregation
from what is expected from the hypothetical mechanism.
The second part of the thesis discusses the GOM circulation and how it may eliminate
copepod patches. The summertime mean surface circulation and eddy kinetic
energy are computed from a Lagrangian drifter dataset and an adaptive technique
that allows for higher spatial resolution while also keeping uncertainty low. Eddy diffusivity
is also computed over different regions of the GOM in an attempt to quantify
the spreading of a patch of copepods, and is found to be lower near the coast where
right whales are often found feeding on copepod patches. In the next chapter, a numerical
drifter dataset is used to understand how the results of the previous chapter
depend upon the quantity of observations. It is found that the uncertainty in estimating eddy diffusivity is tightly coupled to the number of drifters in the calculation.
Description:
This work was supported by the WHOI Coastal Ocean Institute Graduate Student
Fellowship and Student Research Award, the WHOI Academic Programs O ce, the
NOAA National Marine Fisheries Service Northeast Fisheries Science Center (NOAA
Cooperative Agreement NA09OAR4320129), and the O ce of Naval Research Marine
Mammals and Biology Program (Grant N00014-12-1-0208).
Keywords:
Ocean circulation
;
Zooplankton
Repository Name:
Woods Hole Open Access Server
Type:
Thesis
Format:
application/pdf
