Monday, 10 January 2005: 9:15 AM
Is there a Bi-Polar Seesaw?
The Manabe Climate Model (MCM) is used to study the so-call bi-polar seesaw. In ice records obtained from Antarctica and Greenland, it has been noted that when one hemisphere is warm, the other hemisphere is cold and viscera. Here this topic is investigated in an idealized way. The GFDL R30 atmosphere-ocean model is forced with a freshwater anomaly of 1 SV for 100 model years. After 100 years, this additional freshwater is turned off and the model climate is allowed to recover. In one integration, the freshwater is input into high latitudes of the N Atlantic Ocean. In the second integration, the freshwater is put into high latitudes of the Southern Ocean.
In both cases, oceanic convection and the associated thermohaline circulation (THC) local to the freshwater input is greatly hindered and slowed down. This results in a large local cooling and freshening of the surface waters. The hemisphere with the freshwater input tends to cool at the surface, while the opposite hemisphere tends to warm. This supports the seesaw hypothesis. However, the response of most the climate system is much more complicated. These features will be discussed.