Biogeochemical Implications of Recent Changes in the Ventilation of the Japan/East Sea
Abstract
The Japan/East Sea (JES) is a highly productive marine ecosystem that constitutes an important fisheries resource for a number of nations. As a weakly stratified marginal sea separated from the Pacific Ocean by shallow straits, the ventilation of the abyssal JES is remarkably susceptible to climate change. Not surprisingly, such changes have indeed been noted for the late-glacial and Holocene. Over the past half-century or more, there has been a trend toward increasing deep water temperatures, increasing dissolved inorganic nutrients, and decreasing dissolved oxygen levels that are consistent with a reduction in deep ventilation in recent decades. I present a minimum complexity model of the Japan Sea that utilize observations of the transient tracers CFCs, tritium, and 3He to place useful constraints on the character, magnitude, and timing of these changes. I describe these changes within the context of differing mechanisms for deep water formation and ventilation. The converse of ventilation is the return of deep nutrients to the surface ocean, which in turn forms the basis of the food pyramid, and hence the support for new primary production in this strategically important marginal sea. The tracer constrained model calculations suggest that the primary (convective) supply of inorganic nitrogen to the shallow JES reduced by nearly a factor of two (from 1.7 to 0.9 Tmoles) in the latter half of the 20^th century. I relate the changes in abyssal nutrient reflux to climatic modulation of water mass formation changes, and present the implications for water column remineralization processes. The implications of the large scale changes for the sustenance of fishery stocks is significant.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFMOS33D..07J
- Keywords:
-
- 4513 Decadal ocean variability (1616;
- 1635;
- 3305;
- 4215);
- 4805 Biogeochemical cycles;
- processes;
- and modeling (0412;
- 0414;
- 0793;
- 1615;
- 4806 Carbon cycling (0428);
- 4808 Chemical tracers;
- 4845 Nutrients and nutrient cycling (0470;
- 1050)