Wednesday, November 11, 2015

Book Review: Climate and the Oceans

Climate and the Oceans, by Geoffrey K. Vallis, is the third book of the Princeton Climate Primer series that I am reviewing. Like the others, this is available in economical Kindle and paperback editions.

Vallis's book is heavily focused on the dynamics of the ocean, but contains introductory sections on climate, numerous other examples of climate effects, including El Niño. The final chapter is devoted to global warming, and a discussion of the greenhouse effect. He emphasizes the uncertainties that remain both in the ocean dynamics and more generally. Alternative theories of global warming (solar effects, novel cyclical mechanisms, etc.) but emphasizes that there is essentially zero evidence for any of these.

Ocean dynamics is fluid dynamics on a rotating, wind blown, unevenly heated sphere, with complicated salinity effects thrown in. In other words, it's complicated as all get out. Vallis takes on the task of explaining the complicated mixture of wind, Coriolis, and Eckman transport effects responsible for the major currents in the ocean without explicit appeal to vector calculus - a somewhat unfortunate choice, in my opinion, since explicit appeal to vorticity (the curl of velocity) makes things quite a bit clearer in my mind, but I found the explanations pretty clear considering the limitation to just partial derivatives.

Some mathematical details are relegated to chapter appendices.

One example stands out as something he clarified for me: deep ocean current that sinks in the North Atlantic and rises in the Antarctic. That always seemed counter intuitive to me, since the coldest water is in Antarctica. The explanation lies in the fact that 1) North Atlantic water has higher salinity and 2) the fact that the circumpolar winds around the Southern continent drive an Eckman transport of surface water toward the North, so Eckman pumping is the key.

Overall, an excellent book, and another worthy title in the Princeton Climate Primer series. If you need a more extensive and mathematical dose of fluid dynamics on a differentially heated rotating sphere, Vallis has also written a serious textbook: Atmospheric and Oceanic Fluid Dynamics: Fundamentals and Large Scale Circulation.