Methane in coastal sea water, sea ice, and bottom sediments, Beaufort Sea, Alaska

This report summarizes data acquired from 1990 to 1994 for
the gas-hydrate portion of the USGS project "Permafrost
and gas hydrate as possible sources of methane" of the
USGS Global Change and Climate History program. The
objective of this project has been to test the hypothesis
that gas hydrate deposits of the Beaufort Sea continental
shelf are destabilized by the ~10°C temperature increase
that has resulted from the Holocene transgression of the
Arctic Ocean. To test this idea we have selected an area
off the north coast of Alaska centered on Harrison Bay. We
have measured the concentration of methane in surficial
sediments, in the water column when ice is present and
absent, and in seasonal sea ice. Our results show that
more methane is present in the water when ice is present
than when ice is absent, and that methane is also present
within the ice itself, often at higher concentrations than
in the water. Thus the Beaufort Sea shelf of Alaska is a
seasonal source of methane. The primary source of this
methane has not yet been defined, but gas hydrate is a
reasonable candidate.