1994 Arctic Ocean Section
10
trations were also relatively high in
a. Surface Water
cracks (openings in the multi-year
8
ice). These cracks, called leads, tend
6
to be narrow (tens to hundreds of
4
meters in width) but may extend for
2
many kilometers. In some situations
leads may reach several kilometers in
0
30
width and are termed polynyas. Of
b. Bottom Ice
the ice habitats, the highest algal bio-
mass and DMS concentrations were
20
found in the bottom of the ice on the
eastern side of the transect. On a vol-
10
ume basis, the maximum DMS con-
centrations were three times higher
0
in the bottom of the ice than in sur-
5
c. Sub-ice
face water. Significant DMS concen-
4
trations were also measured in the al-
3
gal mats loosely attached to the bot-
2
tom surface of the ice. These mats,
1
composed of the centric diatom
0
Melosira sp., were found mostly in the
Canada Basin (from 75 to 80N and
2.5
from 86 to 88N) and in the Maka-
d. Melt Pools
2.0
rov Basin (from 89 to 90N). We
1.5
also measured detectable levels of
1.0
DMS in melt pools, which covered
0.5
up to 20% of the surface of the ice.
These results indicate that physical
0
70
80
90
80
North Latitude
and biological processes occurring at
Latitudinal changes of the DMS concentra-
the marginal ice zone of the Chuk-
tion in surface water, in the bottom of the ice,
chi Sea favor DMS production. In the
at the waterice interface and in melt pools
ice-covered central Arctic, although
in the Arctic Ocean in the summer of 1994.
local sources of DMS exist, DMS
sea-to-air fluxes are probably limited by the gas-tight ice cover. At these high
atmosphere through leads and other openings in the ice cover.
44
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