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Impact of Large-scale Tropical Precipitation Anomalies on the Overturning and Interior Watermass Structure of a Coupled Climate Model
Matthew Harrison, Robert Hallberg, Alistair Adcroft
NOAA GFDL
(Abstract received 05/12/2009 for session X)
ABSTRACT
The Walker cell in GFDL\'s CM2-class of coupled climate models is shifted zonally, with too little precipitation over the Amazon and Atlantic and too much precipitation over Africa and Indonesia. This talk examines the long-term evolution in CM2G of the overturning strength and abyssal and near-surface watermass properties when this bias is forcibly corrected. It is demonstrated that this tropical precipitation bias is a leading cause of the long-term interior watermass biases in CM2G. When the precipitation in the tropical Atlantic is increased and that over Indonesia decreased, the Atlantic overturning slows markedly and both cools and freshens for about a century. The Southern Ocean is impacted as modified NADW is entrained into CDW/AAIW. The upper ocean becomes saltier over most of the globe with the exception of the tropical and North Atlantic. This acts to increase upper intermediate watermass production at the expense of lighter subtropical water.
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2009 LOM Workshop, Miami, Florida Jume 1 - 3, 2009