Scientists uncover more evidence of Arctic warming
February 17th, 2009 by Jim JustScientists are uncovering new evidence that global warming is already having profound impacts on the Arctic.
Teams of scientists working on the Census of Marine Life – a 10-year project involving researchers in more than 80 nations that aims to chart the diversity, distribution and abundance of life in the oceans – have found that global warming is changing the distribution, abundance, and diversity of marine life in the polar seas with profound implications for creatures further up the food chain. The loss of sea ice cover means the loss of the sea ice algae, small animals and crustaceans which depend on it. The complete loss of summer ice – which scientists now think could occur within 20 years – will lead to a complete change in the ecosystem – salinity, ice melt, flow, currents.
Finnish scientists report that the Arctic is belching out nitrous oxide – a greenhouse gas 310 times more potent than CO2 and 11 times more persistent in the atmosphere than methane. Nitrous oxide releases create a positive feedback loop: increasing temperatures cause increased releases of the gas, which in turn further increases temperatures. Climate Feedback also has a piece on the Finnish research.
Scientists have discovered that another feedback loop is kicking in. For the first time, research has confirmed that the Southern Ocean can no longer absorb as much atmospheric CO2 as before. Its role as a ‘carbon sink’ has been weakened, and it may now be only one-tenth as efficient as previously estimated. The same trend can be observed at high latitudes in the North Atlantic.
This decrease in the ability of the oceans to absorb carbon is the result of climate change at high latitudes, which has led to an increase in the relative difference of atmospheric pressure at latitudes between 40 and 60° S, and therefore to higher wind speeds, leading in turn to increased ocean mixing, with surface waters mixing with deep waters. Surface waters contain less CO2 than deep waters, since CO2 is taken up by the photosynthetic activity of marine phytoplankton. In addition, when these organisms die, they are deposited in deep water where they are broken down by bacteria, thus enriching the deep water in CO2. Thus when there is increased wind mixing of the ocean, greater amounts of CO2 are carried from the deep layers to the surface and, as a result, the ocean’s ability to absorb atmospheric CO2 is diminished.
Both in the northern and southern hemispheres, the weakening of oceanic carbon sinks means an increase in atmospheric CO2 content and thus in climate warming. These effects are not yet included in coupled climate/carbon models like those used in the IPCC reports.