Will the East/Japan Sea become an anoxic sea in the next century?

The deep interior of the East/Japan Sea is governed by its unique thermohaline circulation which is far smaller but much faster than the Great Ocean Conveyer Belt. Analysis of oxygen profiles confirms that, at present, less dense waters no longer penetrate to the bottom. Instead they start to generate intermediate waters. Consequently, the volume of each water mass is changing with time. Recently, a Moving-Boundary Box Model (MBBM) of the region, which can accommodate this feature, has been proposed. The model predicts that the current bottom water will be replaced by deep water by the year 2040. The physical supply of dissolved oxygen into the deep waters and the biological oxygen utilization rates in the East Sea are estimated using the MBBM under the structural change of ventilation scenario. The oxygen utilization rates of the deep water masses [Central Water (CW), Deep Water (DW), and Bottom Water (BW)] in the East Sea are estimated as 2.0, 1.1, and 0.8 mumol kg(-1) year(-1), respectively. This study also confirms that the dissolved oxygen concentration of the deep waters in the East Sea has decreased over the years, as recent studies have claimed. However, this trend can only be extended until the year 2040 since the Bottom Water will disappear by then and the deep layer structure will be changed into a two-layer system. Our model suggests that the previous predictions of the imminent anoxic interior of the East Sea will not be realized because the current structural change will replace the bottom water before it becomes hypoxic. (C) 2004 Elsevier B.V. All rights reserved.