Primary Production in a Changing Arctic Ocean
|The CCGS Louis S St.-Laurent about to depart Kugluktuk for the 2013 Joint Ocean Ice Study 2013 cruise. We will be collecting samples for triple oxygen isotopes in order to learn about effect of sea ice melt on biological production. (Photo courtesy of Z. Sandwith)|
Bill Williams (Fisheries and Ocean Canada)
The Arctic Ocean is changing rapidly as the global climate warms. Summer sea-ice extent is dramatically shrinking, with 2012 setting the record low in minimum sea-ice extent. The temperature is rising, the melt season is lengthening, and the freshwater storage and terrigenous input are increasing. How will these continuing changes affect biological productivity in the Arctic Ocean? The answer to this important question is not known. In order to predict future biological productivity and carbon cycling, we need, at least, to know the present-day rates of biological productivity in the Arctic Ocean and to understand what constrains them.
One way to gain such understanding is to quantify rates of Net Community Production and Gross Primary Production. Net Community Production (NCP) is defined as photosynthesis minus community respiration and thus is the net amount of CO2 taken up by the biological pump. Gross Primary Production (GPP) is defined as the total photosynthetic flux and thus is the carbon produced at the base of the food chain. By concurrently measuring rates of NCP and GPP, we can look separately at environmental effects on photosynthesis and respiration. This in turn allows a better mechanistic understanding of the processes controlling biological production. Thus, we are using triple oxygen isotopes and O2/Ar ratios to quantify rates of biological production in 2011, 2012, and currently are collecting samples for 2013. We have found intriguing connections between sea ice melting and rates of biological production.