Vol. 53 - Alaska Resources Library and Information Services

to a great extent tidally driven, there is a net movement of 2.0-5.5
cm sec[superscript]-1
eastward and northward into Bristol Bay. Kinder and Schumacher
(1981b) and Schumacher and Reed (1983) summarized data for current
patterns in the southeastern Bering Sea and showed weak currents of 2-5
cm sec[superscript]
-1
along the NAS and 1-5 cm sec[superscript]-
1
moving northwest over the St.
George Basin (Figure 4.1-3). They stressed that instantaneous flow can
be substantially greater than these averages (up to twenty times greater
than the long-term vector) and the direction quite variable. Cline, et
al. (1981) used methane profiles to calculate current speeds of 7 cm
sec[superscript]
-1
northeast along the NAS and 5 cm sec[superscript]
-1
northwest over the St.
George Basin. Both values are in close agreement with current meter
readings.
In the area of the present red king crab study, Bristol Bay encompasses
two well-defined water masses separated by a frontal system at approximately
the 50 m isobath (Figure 4.1-3; Iverson, et al. 1979, Kinder and
Schumacher 1981b). Shoreward of the 50 m isobath is the coastal domain
where waters are vertically homogeneous and turbulent due to wind and
tidal mixing. There is little horizontal mixing across the density
gradient of the frontal system, particularly at depth, but surface
waters of the coastal domain may deviate from a strict counter clockwise
pattern to move northward across the middle shelf domain in summer (L.K.
Coachman, Dept. Oceanography, U.W., pers. communication).
The middle shelf domain between 50 and 100 m is characterized as a
stratified two-layered system of cold residual water that is heated and
mixed to variable depths by radiation and wind in the spring and summer.
This water mass is portrayed as an essentially stationary barrier that
deflects coastal currents to the northeast toward Kvichak Bay and then
west to Cape Newenham.
The physical properties of these water masses in regard to temperature,
food supply, and rate and direction of currents are of major importance
for assessing their relative value to larval production and survival.
398