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 February 2017
Description:
In this thesis, I use coastal measurements of dissolved O2 and inert gases to provide insight
into the chemical, biological, and physical processes that impact the oceanic cycles of carbon
and dissolved gases. Dissolved O2 concentration and triple isotopic composition trace net and
gross biological productivity. The saturation states of inert gases trace physical processes,
such as air-water gas exchange, temperature change, and mixing, that affect all gases.
First, I developed a field-deployable system that measures Ne, Ar, Kr, and Xe gas
ratios in water. It has precision and accuracy of 1 % or better, enables near-continuous
measurements, and has much lower cost compared to existing laboratory-based methods.
The system will increase the scientific community’s access to use dissolved noble gases as
environmental tracers.
Second, I measured O2 and five noble gases during a cruise in Monterey Bay, California.
I developed a vertical model and found that accurately parameterizing bubble-mediated gas
exchange was necessary to accurately simulate the He and Ne measurements. I present the
first comparison of multiple gas tracer, incubation, and sediment trap-based productivity
estimates in the coastal ocean. Net community production estimated from 15NO –3 uptake
and O2/Ar gave equivalent results at steady state. Underway O2/Ar measurements revealed
submesoscale variability that was not apparent from daily incubations.
Third, I quantified productivity by O2 mass balance and air-water gas exchange by dual
tracer (3He/SF6) release during ice melt in the Bras d’Or Lakes, a Canadian estuary. The
gas transfer velocity at 〉90% ice cover was 6% of the rate for nearly ice-free conditions.
Rates of volumetric gross primary production were similar when the estuary was completely
ice-covered and ice-free, and the ecosystem was on average net autotrophic during ice melt
and net heterotrophic following ice melt. I present a method for incorporating the isotopic
composition of H2O into the O2 isotope-based productivity calculations, which increases the
estimated gross primary production in this study by 46–97%.
In summary, I describe a new noble gas analysis system and apply O2 and inert gas
observations in new ways to study chemical, biological, and physical processes in coastal
waters.
Description:
Research and studies have been supported by funding
from the National Science Foundation (NSF) through grants OCE-8608400 and PLR-
1304406 (to RHR Stanley) and OCE-1129644 (to DP Nicholson), the WHOI Arctic Research
Initiative (funds to RHR Stanley and B Loose), a WHOI Innovative Technology grant (to
RHR Stanley), the WHOI Coastal Ocean Institute (Student Research Fund to CC Manning),
the WHOI Academic Programs Office (including an Ocean Ventures Fund grant to CC Manning),
and the Houghton Fund at MIT. I received scholarships from the National Sciences
and Engineering Research Council of Canada (NSERC) and the Canadian Meteorological
and Oceanographic Society (CMOS).
Keywords:
Gases
;
Chemical oceanography
;
Western Flyer (Ship) Cruise
Repository Name:
Woods Hole Open Access Server
Type:
Thesis
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