Meridional reorganizations of marine and terrestrial productivity during Heinrich events

HR: 10:35h
AN: PP12A-02 [Abstracts]
TI: Meridional reorganizations of marine and terrestrial productivity during Heinrich events
AU: * Menviel, L
EM: menviel@hawaii.edu
AF: Department of Oceanography, University of Hawai'i, Honolulu, HI 96822, United States
AU: Timmermann, A
EM: axel@hawaii.edu
AF: IPRC, University of Hawai'i, Honolulu, HI 96822, United States
AU: Mouchet, A
EM: A.Mouchet@ulg.ac.be
AF: Departement AGO, Universite de Liege, Liege, B-4000, Belgium
AU: Timm, O
EM: timm@hawaii.edu
AF: IPRC, University of Hawai'i, Honolulu, HI 96822, United States
AB: To study the response of the global carbon cycle to a weakening of the Atlantic Meridional Overturning Circulation (AMOC) a series of freshwater perturbation experiments is conducted both, under pre-industrial and glacial conditions using the earth system model of intermediate complexity LOVECLIM. A shutdown of the AMOC leads to substantial cooling of the North Atlantic, a weak warming of the southern hemisphere, intensification of the northeasterly trade winds and a southward shift of the Intertropical Convergence Zone (ITCZ). Trade wind anomalies change upwelling in the tropical oceans and hence marine productivity. Furthermore, hydrological changes associated with a southward displacement of the ITCZ, lead to a reduction of terrestrial carbon stocks mainly in northern Africa and northern South America, in agreement with paleo-proxy data. In the freshwater perturbation experiments, the ocean acts as a sink of CO₂, primarily through increased solubility. The net atmospheric CO₂ anomaly induced by a shutdown of the AMOC amounts to about +15 ppmv and --10 ppmv for pre-industrial and glacial conditions, respectively. This background state dependence can be explained by the fact that the glacial climate is drier and the terrestrial vegetation therefore releases a smaller amount of carbon to the atmosphere. This study demonstrates that the net CO₂ response to large-scale ocean circulation changes has significant contributions both, from the terrestrial and marine carbon cycle.
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 1620 Climate dynamics (0429, 3309)
DE: 4962 Thermohaline
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting