On the non‐linear response of the ocean thermohaline circulation to global deforestation

An experiment of 1750-yr duration has been performed with a three-dimensional coupled atmosphere-sea-ice-ocean-vegetation model to study the transient effect of global deforestation on climate. The response consists of two phases. First, the initial global cooling due to increased surface albedo (forest replaced by grassland) is enhanced by a significant expansion of the sea-ice cover in both hemispheres, which increases the surface albedo further. Second, a non-linear response of the ocean thermohaline circulation results in a southward shift of the main deep-convection site and reduced northward heat transport in the Atlantic Ocean, leading to enhanced global cooling due to a further expansion of Arctic sea ice. Ultimately, surface temperatures over northwestern North America become sufficiently low to prevent the snow pack to melt in summer. Our results thus suggest that large-scale changes in forest cover may lead to non-linear changes in the climate system.

[1]  H. Goosse,et al.  Potential causes of abrupt climate events: A numerical study with a three‐dimensional climate model , 2002 .

[2]  A. Kattenberg,et al.  ECBILT: a dynamic alternative to mixed boundary conditions in ocean models , 1998 .

[3]  T. Fichefet,et al.  Modeling the effect of freshwater pulses on the early Holocene climate: the influence of high-frequency climate variability , 2002 .

[4]  H. Goosse,et al.  Decadal variability in high northern latitudes as simulated by an intermediate-complexity climate model , 2001, Annals of Glaciology.

[5]  Hugues Goosse,et al.  Importance of ice-ocean interactions for the global ocean circulation: A model study , 1999 .

[6]  John H. C. Gash,et al.  Amazonian deforestation and climate , 1997 .

[7]  Tim N. Palmer,et al.  Physical Climate Processes and Feedbacks , 2001 .

[8]  T. Fichefet,et al.  The 8.2 kyr BP event simulated by a Global Atmosphere—Sea‐Ice—Ocean Model , 2001 .

[9]  Victor Brovkin,et al.  Carbon cycle, vegetation, and climate dynamics in the Holocene: Experiments with the CLIMBER‐2 model , 2002 .

[10]  J. Raine,et al.  Indication of Global Deforestation at the Cretaceous-Tertiary Boundary by New Zealand Fern Spike , 2001, Science.

[11]  Andrea N. Hahmann,et al.  RCCM2–BATS Model over Tropical South America: Applications to Tropical Deforestation , 1997 .

[12]  H. Goosse,et al.  A mechanism of decadal variability of the sea-ice volume in the Northern Hemisphere , 2002 .

[13]  F. Selten,et al.  Intrinsic limits to predictability of abrupt regional climate change in IPCC SRES scenarios , 2002 .

[14]  A two‐phase response of the Southern Ocean to an increase in greenhouse gas concentrations , 2001 .

[15]  L. Mysak,et al.  Response of the thermohaline circulation to cold climates , 2002 .

[16]  Shunji Murai,et al.  Modelling for prediction of global deforestation based on the growth of human population , 1999 .

[17]  S. Baum,et al.  Effect of vegetation on an ice-age climate model simulation , 1997 .

[18]  P. Rowntree,et al.  Understanding the Sensitivity of a GCM Simulation of Amazonian Deforestation to the Specification of Vegetation and Soil Characteristics , 1997 .

[19]  Victor Brovkin,et al.  Biogeophysical versus biogeochemical feedbacks of large‐scale land cover change , 2001 .