(^) (After Martin & Fitzwater 1988.)
The subarctic Pacific region is a cyclonic gyre, with the North Pacific west wind
drift moving along the southern side in a broad band north of ∼40°N. This flow turns
offshore of North America into the Alaska Stream, carrying water north then west
around the coast of the Gulf of Alaska and Aleutian Island chain. Return flow into the
west wind drift occurs along Kamchatka and Hokkaido as the Oyashio Current meets
and turns eastward as it encounters and mixes in a strong eddy field with the Kuroshio
flowing north along Honshu. There is also exchange near the dateline between the
westbound northern limb and west wind drift, amounting to a separation of western
and eastern subarctic gyres. The cyclonic circulation creates doming of density
isopleths in the gyre centers that should correspond to upward Ekman transport.
However, the entire region is also characterized by a surface layer of reduced salinity,
S ≈ 33 down to a halocline (Fig. 11.3) at 80 to 120 m (variation from internal waves),
where it increases to S ≈ 34. The southern limit of the region is often defined as the
line running west to east where the S = 34 isohaline rises to the surface. The low
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