OCEAN RESPONSE TO SURFACE HEAT ANOMALIES

An ocean general circulation model (OGCM) is used to study the respons e of ocean heat and mass transport to positive and negative heat flux anomalies at the ocean surface. As expected, tropical and low-latitude mixed layers respond rapidly (e-folding time about 50-70 years) to ex ternal forcing, while the response of the high-latitude mixed layer, e specially the Southern Ocean and northern North Atlantic, is very slow (e-folding time greater than 300 yr). The overall response is faster for negative than positive heat flux anomaly at the surface. The merid ional heat transport changes by 15% in the first 50 yr in the southern high latitudes. Surprisingly, for the next 400-500 yr the change is v ery small. The analysis shows that the meridional mass transport inten sifies in response to a negative surface heat flux anomaly but weakens in response to a positive heat flux anomaly. For example, at model ye ar 100 the NADW is reduced from about 18 Sv to about 10 Sv for the pos itive heat flux experiment but increased to about 26 Sv for the negati ve heat flux experiment.