Ocean science questions ANSWERED! post 1 - Temperature rising

I wanted a little exercise to help me study for my comprehensive exams in my PhD program in Marine Science.  So i asked you all to write to me with your burning ocean science question, and i will answer right away, in practice for the exam.  Here are some of the q's and a's.

Q:  How does the rise in global temperatures affect the carbon-carrying capacity of the oceans? Can you quantify this? (Bruce)

               

A: Yes!  This is an important component of ocean acidification.  OA is the process whereby the ocean becomes more acidic with increasing carbon dioxide (CO2) in the atmosphere.  Ocean acidification is an impact to the carbon system, or carbon cycle.  There is no “carrying capacity” of carbon in the ocean per se; that is, it is unknown how much carbon the ocean could store or sequester.  The ocean is the largest sink (sequestration site) of CO2, for any entity in continual contact with the atmosphere; the ocean captures and stores about 1/3 of the human-produced carbon dioxide today. This is due to phytoplankton taking CO2 in and eventually sinking (in one form or another) to the bottom and becoming sediment.  The way temperature works into all of this is twofold.  First, CO2 is a greenhouse gas.  This means that the more CO2 there is the atmosphere, the more solar radiation will be trapped in the atmosphere, and the warmer the temperature will get at the surface of the Earth.  So it’s a tidy little feedback loop.  Second, temperature affects the solubility of gases (the amount of the gas that can be present in the water).  Higher temperature means less gas solubility.  This isn’t so much a “problem” for absorbing CO2, and transporting to the sediment, since higher temps will mean less CO2 in the water, but it is a problem for absorbing oxygen!  Higher temperatures mean that over the long term, less oxygen-rich waters will be formed, and oxygen rich waters are one of the VERY important components of fueling phytoplankton growth in the most productive parts of the ocean. 

               So to answer your question, yes, rising temperature definitely impacts the ability of the ocean to sequester carbon dioxide.  And yes, we can measure it!  Doney et al (2009) provide an excellent review of the carbon cycle in the ocean, and how rising CO2 levels can be measured.  Measuring global temperature is continually occurring, and is also accomplished by measuring levels of greenhouse gases in the atmosphere.