. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder. Oceanography Bering Figure 27-3. Dissolved methane (nl/1, STP) along a north- south section through Unimak Pass. Observations were made in 1975. shown in Figs. 27-4a and b. At the beginning of the observations (Sta. 46), the distribution of methane was veriiically homogeneous, or nearly so. At approx- imately 4 hours, methane concentration in the sur- face layers increased to over 200 nl/1 and remained high for the following 20 hours. Similar trends were observed at depth
. The Eastern Bering Sea Shelf : oceanography and resources / edited by Donald W. Hood and John A. Calder. Oceanography Bering Figure 27-3. Dissolved methane (nl/1, STP) along a north- south section through Unimak Pass. Observations were made in 1975. shown in Figs. 27-4a and b. At the beginning of the observations (Sta. 46), the distribution of methane was veriiically homogeneous, or nearly so. At approx- imately 4 hours, methane concentration in the sur- face layers increased to over 200 nl/1 and remained high for the following 20 hours. Similar trends were observed at depth although there appeared to be a sig- nificant lag period (four to five hours). Because the only reasonable source of the methane is St. George Basin, it is assumed that during the observational peri- od water was advecting south through Unimak Pass. To the north at Station Ebb 37, just east of the Pribilof Islands, the concentration of methane at the surface and at depth was uniform over the entire ob- servational period. This suggests that methane-rich water from St. George Basin did not move onto the shelf during this period. On the contrary, the mean current trajectory was probably parallel to the iso- baths and would result in advection of dissolved methane toward the northwest (Coachman and Char- nell 1979). In contrast to conditions observed the previous fall, concentrations of all LMW hydrocarbons were elevated in the surface waters during July. Concen- tration of dissolved methane in the surface waters is shown in Fig. 27-5a. Port MoUer once again was a significant source, as it was the previous fall. A con- centration of methane greater than 1300 nl/1 was ob- served at Station 28, or a value approximately 26 times the saturation amount. The source of this methane is believed to be sediments rich in organic matter inside Port MoUer, where decomposition of vegetable matter could result in the vigorous produc-. "04 < 12 16 20 24 TIME (hrs) STA Ebb 37. Please note
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