Estimates of non-tidal exchange transport between the Sea of Okhotsk and the North Pacific |
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| Authors: | Katsuro Katsumata Ichiro Yasuda |
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| Institution: | (1) Institute of Marine Geology and Chemistry, National Sun Yat-Sen University, Kaohsiung, 804, Taiwan, R.O.C.;(2) Pacific Oceanological Institute Far Eastern Branch, Russian Academy of Sciences, Vladivostok, Russia;(3) OCEAN Laboratory/RIO, SEES, Seoul National University, Shilim-Dong, Gwanak-Gu, Seoul, 151-747, Korea;(4) Frontier Observational Research System for Global Change, International Arctic Research Center, University of Alaska Fairbanks, Fairbanks, AK, 99775-7335, U.S.A |
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| Abstract: | The outflow from the Sea of Okhotsk to the North Pacific is important in characterising the surface-to-intermediate-depth
water masses in the Pacific Ocean. The two basins are separated by the Kuril Islands with numerous straits, among which the
Bussol and the Kruzenshterna Straits are deeper than 1000 m. The physics governing the transport between the two basins is
complicated, but when the semidiurnal and diurnal tides are subtracted, the observed density and velocity structures across
the Bussol Strait suggest a significant contribution from geostrophic balance. Using a two-layer model with the interface
at 27.5σ
θ
, part of the upper layer transport that is not driven by tides is estimated using two previously unexplored data sets: outputs
from the Ocean General Circulation Model for Earth Simulator (OFES), and historical hydrographic data. The Pacific water flows
into the Sea of Okhotsk through the northeastern straits. The greatest inflow is through the Kruzenshtern Strait, but the
OFES results show that the contributions from other shallower straits are almost half of the Kruzenshtern inflow. Similarly,
the outflow from the Sea of Okhotsk is through the southwestern straits of the Kuril Islands with the largest Bussol Strait
contributing 60% of the total outflow. The OFES and hydrographic estimates agree that the exchange is strongest in February
to March, with an inflow of about −6 to −12 Sv (negative indicates the flow from the North Pacific, 1 Sv = 106 m3s−1), and an outflow from the Sea of Okhotsk of about +8 to +9 Sv (positive indicates the flow from the Sea of Okhotsk), which
is weakest in summer (−3 to +1 Sv through the northeastern straits and +0 to +3 Sv through the southwestern straits). The
estimated seasonal variation is consistent with a simple analytic model driven by the difference in sea surface height between
the two basins. |
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