LONG-TERM COORDINATED CHANGES IN THE CONVECTIVE ACTIVITY OF THE NORTH ATLANTIC
ROBERT DICKSON, JOHN LAZIER!, JENS MEINCKE 2 and PETER RHINES 3
MAFF Fisheries Laboratory
LowestoJt, Suffolk, England
Contents
1 Indroduction
211
2 Variability of deep convection in the Greenland Sea, and its controls
213
2.1 General description. . . . . . . .. . . . . . . .
213
2.2 Time-dependence of GSDW characteristics . . . . . . . . .
214
2.3 Causes of change in Greenland Sea Convection . . . . . . .
216
2.4 Remote Effects on the Deep Waters of the Norwegian Sea.
221
3 Ventilation of the West Atlantic and its causes
225
3.1
Changes in the North Atlantic Oscillation, and the Storm Climate of the West
Atlantic . . . . . . . . . . . . . . . . . . .
225
3.2 Effect on ventilation of the west Atlantic . . . . . . . . . . . . . . . . . .
229
4 Variability of Deep Convection in the Labrador Sea, and its Controls
235
4.1 The remote effects of the NAO minimum . . . . . . . .
235
4.2 The restoration of deep convection in the Labrador Sea
4.3 The link with air temperature . . . . . . . . . . . . . . .
4.4 Changes in LSW density . . . . . . . . . . . . . . . . . .
4.5 Time dependence in the advective sublayer at OWS BRAVO
4.6 The spreading of Labrador Sea Water . . . . . . . . . . . . .
5 Summary and Conclusions
1 Indroduction
238
240
242
247
247
253
The North Atlantic is a peculiarly convective ocean. The convective renewal of intermediate and deep waters in the Labrador Sea and Greenland/
Iceland Sea both contribute significantly to the production and export of
North Atlantic Deep Water, thus helping to drive the global thermohaline circulation, while the formation and spreading of I8-degree water at
1 Bedford Institute of Oceanography, Dartmouth, Canada
2Institut fiir Meereskunde, Hamburg, Germany
3School of Oceanography, University of Washington, Seattle, USA
NATO ASI Series, Vol. I44
Decadal Climate Variability
Dynamics and Predictability
Edited by David L. T. Anderson and Jiirgen Willebrand
© Springer-Verlag Berlin Heidelberg 1996