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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999

FROM VOLUME 12, NUMBER 4, APRIL 1999

JOURNAL ARTICLES...
OCEAN STRUCTURE AND TEMPERATURE

Item #d99apr17

“A Simple Predictive Model for the Structure of the Oceanic Pycnocline,” A. Gnandesikan,Science 283 (5410), 2077-2079 (1999).

A model that relates (1) pycnocline depth, (2) Northern Hemisphere sinking of ocean waters, and (3) low- latitude upwelling to (1) pycnocline diffusivity and (2) Southern Ocean winds and eddies was used to predict large-scale oceanic circulation. It indicated that Southern Ocean processes, such as vertical diffusion, low-latitude upwelling, conversion of light to dense water, winds, and eddies, help maintain the structure of the Earth’s oceans and that pycnocline diffusion controls low-latitude upwelling.

Item #d99apr18

“Glacial-Interglacial Changes in Ocean Surface Conditions in the Southern Hemisphere,” F. Vimeux et al., Nature 398, 410-413 (1999).

Excess deuterium was studied in ice core from Vostok, Antarctica, covering the past 150,000 years. The excess deuterium shows a strong anticorrelation with the Earth’s orbital obliquity, which is attributed to latitudinal changes in insolation and subsequent delivery of moisture to Antarctica. A high excess of deuterium is also associated with cold stage 5d, which is attributed to relatively less moisture from high latitudes and more from low latitudes, reflecting ocean surface conditions and circulation in the Southern Hemisphere.

Item #d99apr19

“Cool Surface Waters of the Subtropical North Pacific Ocean During the Last Glacial,” K. I. Lee and N. C. Slowey,Nature 397, 512-514 (1999).

Shallow-water sedimentary cores from a location with high deposition rates near Hawaii were used to estimate the glacial-period sea-surface temperature (SST) of the subtropical North Pacific by the distribution of oxygen isotopes and by species assemblages of planktonic foraminifera. The results indicated that the annual average SST of the region during the last glaciation was about 2° C cooler than it is today. These results contradict the findings of the CLIMAP project, which indicated that the Pacific was warmer during glaciation that it is today.