Wednesday, October 23, 2013
Environmental Science and Engineering Seminar
The role of oceans in setting climate sensitivity and radiative feedbacks
Brian Rose, Assistant Professor, Department of Atmospheric and Environmental Sciences, University at Albany, SUNY
The oceans take up vast amounts of energy in the tropics and release it to the atmosphere at higher latitudes. The spatial pattern of these sea surface heat fluxes change over time due to both transient heat uptake and long-term rearrangement of the circulation. I discuss fundamental reasons why this spatial pattern of heating / cooling matters to the climate system, e.g. how oceans affect global mean temperature and its pole-to-equator distribution. I use suites of atmospheric models to study the equilibrium climate response to simple patterns of sea surface heating / cooling. I show, for example, that the temperature change associated with a tropical energy source is more than 3 times smaller than the response to the same energy source located at high latitudes. A multi-model analysis shows that tropical ocean heat uptake excites a much more negative radiative feedback with a fundamentally different spatial pattern than is found for either greenhouse gas forcing or high-latitude ocean heat uptake. Both longwave clear-sky and shortwave cloud processes contribute robustly to this difference in sensitivity. I will discuss dynamical and thermodynamical reasons for the robustness of this difference, along with implications for understanding the role of the oceans in climate on various timescales.