To compare the rates of isotherm movement between different ocean regions and at different time scales and to examine to what extent the implied movement is uniform or sporadic.
Type of Study:
Historical observations and model simulation
Long-term warming implies poleward shifts of isotherms in almost all regions. At present on decadal and longer timescales changes due to low frequency natural SST variability can dominate over human-induced changes. Median isotherm shift speeds will be 7 times faster in the 21st Century compared to the 20th Century. SST warming will be greater in the summer in most oceanic regionss. Isotherms often exhibit erratic migration rates over time, even under uniform warming. Species ranges therefore also expected to undergo suddent rapid shifts rather than gradual monotonic poleward movement.
Historical simulations and future projections (2100) of surface and subsurface temperature
Careful consideration needs to be given to regional, temporal and scale differences in thermal habitat movement before attributing poleward migration of species to anthropogenic warming.
Models taking part in the Coupled Model Intercomparison Project phase 5
Response variable :
Temperature, isotherm speeds (geographic shifts of isotherms over time)
Sen Gupta A., Brown J. N., Jourdain N. C., van Sebille E., Ganachaud A. & Vergés A. (In press) Episodic and non-uniform migration of thermal habitats in a warming ocean. Deep Sea Research Part II: Topical Studies in Oceanography.