It’s Boxing Day, the turkey
sandwiches are flowing, the family arguments are reaching a near Shakespearian
conclusion, and the drinking is continuing.
As usual, Father Christmas had a successful flight the other night, and
it seems appropriate in this festive blog post to focus on river discharge in
the Arctic, Father Christmas’ homeland.
Examination of 1936 to 1999 river
discharge data by Peterson, et al. (2002) shows a 7% increase in average annual
discharge of freshwater from the six largest Eurasian rivers that flow into the
Arctic Ocean. This change was correlated with changes in global mean surface
air temperature, and the authors concluding that these changes could have a
significant effect on thermohaline circulation in the Atlantic Ocean in the
future. Quite as to why this increasing trend has occurred is unclear, however McClelleand, et al. (2004) suggest four possible causes of this change: 1.
Increased moisture transport to higher latitudes in a warming climate; 2. Dam
construction and operation; 3. Permafrost thaw; and 4. Increasing forest fires.
Through a combination of observation and monitoring, they suggest that dam
construction, permafrost thaw and forest fires are all unlikely to be responsible
for changes in discharge, sensitivity analysis showing that the changes
required to enact current changes in discharge are unrealistic. Ultimately it is
suggested that increased moisture transport to higher latitudes from global
warming is the most likely conclusion, though there is great uncertainty.
This hypothesis is echoed by the
work of Wu, et al. (2005) who examine human influence upon changing Arctic
discharges. In running a complex climate
model to simulate arctic flows (HadCM3), they show that a model not forced with
anthropogenic factors does not produce the increases in discharge that have
been observed in the Arctic. Increasing
higher latitude precipitation as a result of anthropogenic warming is the most
likely factor to have forced increases in Arctic discharge. It is very
important we try and quantify these changes - a shut down in thermohaline
circulation in the North Atlantic would have catastrophic effects upon our
world’s climate.
At least Santa is surviving so far.
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