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Long-term potential ecosystem responses to greenhouse gas-induced thermohaline circulation collapse


Paul A. T. Higgins, tel. +1 (510) 717 4088, e-mail:


Abrupt climate change, such as could occur with significant thermohaline circulation (THC) weakening, appears throughout the palaeoclimate record and in many model experiments. We examine potential responses of ecosystem structure and function to the combined influence of THC collapse and greenhouse gas increase in Central England using a broad range of temperature scenarios. We demonstrate that biological communities in the North Atlantic region could be heavily influenced by THC collapse, but that the pattern of ecosystem responses depends upon the seasonal pattern of temperature changes. Plausible THC collapse scenarios threaten the remnant habitat fragments, upon which much of England's remaining biodiversity depends, by causing shifts away from the currently dominant temperate broadleaf cold deciduous tree type. Furthermore, some ecosystem responses, particularly of energy partitioning between sensible and latent heat fluxes, constitute potentially substantial feedbacks to the local climate system. However, accurate assessment of biotic responses to THC collapse requires far better confidence of the resulting seasonal temperature cycle than climate models currently provide.

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