PAOC Colloquium: Alison Gray (Princeton)

New insights into the carbon cycle and overturning circulation in the Southern Ocean The southern limb of the global meridional overturning circulation

The southern limb of the global meridional overturning circulation has a critical impact on the climate system by regulating the air-sea balance of carbon dioxide (CO2) and shaping biological production throughout the tropics and subtropics. However, observations of this region have historically been limited in both space and time. Here we present estimates of the seasonal cycle of air-sea CO 2 ux in the Southern Ocean during 2014-2017 computed from measurements collected by new autonomous biogeochemical proling oats. Signicant outgassing of CO2 from the ocean to the atmosphere is observed in the sub polar region during wintertime resulting in a much greater annual net flux than is found in previous observational estimates and most global climate models. Potential drivers of this surprisingly large outgassing signal are discussed and recent work investigating the upwelling of deep waters in the Southern Ocean is used to highlight the role of the three-dimensional overturning circulation. The implications of this nding for climate modeling and for our understanding of the global carbon cycle are considered.

About this Series

The PAOC Colloquium is a weekly interdisciplinary seminar series that brings together the whole PAOC community. Seminar topics include all research concerning the physics, chemistry, and biology of the atmospheres, oceans and climate, but also talks about e.g. societal impacts of climatic processes. The seminars generally take place on Monday from 12-1pm. Lunch is provided to encourage students and post-docs to meet with the speaker. Besides the seminar and lunch, individual meetings with professors, post-docs, and students are arranged.