Slide 19: Thermal indicators: Sea temperatures
Sea temperatures have been gradually increasing worldwide.
Measurements in the 19th century were somewhat inaccurate due to the leaky buckets in which deep water was gathered, but a correction factor used in the calculation of these temperatures shows them to be relatively consistent in the extent of this error, which can hence be eliminated.
Immediate effects of global sea temperature rise will include a change in the capacity of seawater to absorb CO2, reducing its capacity as a carbon sink.
Long term concerns of such a trend include the shutting down or movement of oceanic currents such as the thermohaline "conveyor belt", ironically reducing air temperature in polar areas which are currently warmed by the current. Places such as Britain, which is dependent on the Gulf stream for its current climate, may drop in temperature by as much as 3 degrees, although this effect is very localised.
More importantly, the deep saline currents provide many nutrients for surface ecosystems fed by plankton. A reduction in oceanic plankton will limit another important carbon sink, since many species use atmospheric carbon in the formation of their carbonate shells, and subsequently remove the carbon from the climate when they die and sink to the ocean bottom. It may also cause a crash in oceanic biodiversity, since plankton are the oceans main primary producers, and hence the bottom of the food chain.