1994 Arctic Ocean Section
Laboratory on the
Polar Sea equipped
for analysis of atmo-
sphere and ocean
[Photo by Peter
Brickell.]
interests were principally the origins and behavior of naturally produced vol-
atile halocarbons in the upper ocean, the work focused on surface-water
distributions and the results from the equilibration experiments. Initial data
analysis centered on the primary compounds of interest--bromoform (CHBr3),
dibromomethane (CH2Br2) and chloroiodomethane (CH2ClI)--but data are
being processed for other compounds in our suite of analytes, including bromo-
dichloromethane (CHBrCl2), chlorodibromomethane (CHBr2Cl), methyl
iodide (CH3I) and diiodomethane (CH2I2).
The results of the equilibration experiments indicate that the direction of
flux will be from the ocean to the atmosphere, since the water is supersaturated
with respect to the air. The water column is stably stratified, so there is little
downward mixing. Other dissipation processes, such as hydrolysis and substitu-
tion reactions, are relatively slow, so ventilation to the atmosphere is likely to
be the main short-term removal mechanism for any of these dissolved gases in
the seawater.
The results of our seawater measurements during AOS-94 indicate that
some of the halomethane concentrations in the upper water column at these
high latitudes beneath the polar ice pack are relatively high, even during late
summer and early fall. For example, bromoform concentrations at most stations
are equal to or greater than any others that we have previously measured from
spring to autumn in the open ocean waters or beneath the ice of several Arctic
regions, including Baffin Bay, Alert, Resolute Bay, the Beaufort Sea, the Bering
Sea and the Chukchi Sea. It would appear that while temporal variations may
be relatively large in open ocean areas and in regions where the ice cover melts for
part of the year, they may not be as great in permanently ice-covered regions.
The unexpected picture emerging from the AOS-94 expedition--that halo-
methane concentrations remain high beneath the polar ice cap throughout
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