Observational Evidence of Decadal-Scale Variability of the North Atlantic Ocean

SYDNEY LEVITUS1, JOHN I. ANTONOV1, ZHOU ZENGXI2, HARRY DOOLEY3,

VLADIMIR TSERESCHENKOV4, KONSTANTIN SELEMENOV4, AND ANTHONY F.

MICHAELS5

ABSTRACT

Temperature and salinity time series 27 to 45 years in length are presented for two locations in the North Atlantic. These data are from Ocean Weather Station "C" (52.75°N, 35.5°W), located in the subarctic gyre, and Station "S" (32.16°N, 64.5°W), located in the subtropical gyre. Decadal-scale variability is evident in the deep ocean as well as the upper ocean at these locations. At Station "S", annual mean temperature at 1750 m depth increased by 0.3°C from 1960 to 1990, with salinity also increasing. At OWS "C" annual mean temperature and salinity in the 1,000-to-1,500 m layer increased on the order of tenths of a degree centigrade and 0.02-0.04 psu respectively between 1966 and 1974. From 1975 to 1985 both these parameters decreased by somewhat larger amounts than the earlier increase. At a minimum, these changes indicate that a redistribution of heat and salt have occurred in the North Atlantic Ocean on decadal time scales.

INTRODUCTION

At the beginning of the twentieth century support for research in the field of physical oceanography was justified by the belief that variability of ocean environmental quantities such as temperature and salinity might be responsible for the interannual variability of fisheries. The International Council for the Exploration of the Sea (ICES) was established at this time (1902) for the purpose of coordinating such studies on an international scale. The governments of the various north European countries that founded ICES recognized the requirement to undertake such studies multi-nationally. Many of the founders of the field of physical oceanography, such as V. W. Ekman and M. Knudsen, were scientific members of this organization.

One of the earliest descriptions of interannual variability

1  

NOAA National Oceanographic Data Center, Washington, D.C.

2  

Department of Meteorology, University of Maryland, College Park, Maryland

3  

International Council for Exploration of the Sea, Copenhagen, Denmark

4  

State Oceanographic Institute, Moscow, Russia

5  

Bermuda Biological Station for Research, Inc., Ferry Reach, Bermuda



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