Rates of thermohaline recovery from freshwater pulses in modern, Last Glacial Maximum, and greenhouse warming climates

• Main Authors: C. M. Bitz, J. C. H. Chiang, W. Cheng, J. J. Barsugli
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2007
• Subjects: North Atlantic; Sea ice
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.522.3272; http://www.atmos.washington.edu/~bitz/basicstate_preprint.pdf

Recovery rates of the thermohaline circulation after a freshwater pulse in the North Atlantic vary consider-ably depending on the background climate, as demon-strated in the Community Climate System Model. The recovery is slowest in a Last Glacial Maximum (LGM) climate, fastest in a modern climate, and intermedi-ate between the two in a greenhouse warming (4XCO2) climate. Previously proposed mechanisms to explain thermohaline circulation stability involving altered hor-izontal freshwater transport in the North Atlantic are consistent with relative recovery rates in the modern and 4XCO2 climates, but fail to explain the slow LGM recovery. Instead, sea ice expansion inhibits deep-water formation after freshening in the LGM climate by re-ducing heat loss to the atmosphere and providing addi-tional surface freshwater. In addition, anomalous verti-cal freshwater transport across ∼1km depth after fresh-ening is most effective at weakening the stratification in the modern case but is negligible in the LGM case. 1.