Fig. 4 A three-dimensional perspective of the subpolar Southern Ocean carbon cycle. A three-dimensional perspective of the subpolar Southern Ocean carbon cycle. Schematic illustration of the subpolar Southern Ocean carbon cycle, with the nearside exactly as in Fig. 1 and extended outward to recognize the crucial role of the horizontal circulation of mid-depth waters and their enrichment in carbon by biological production and remineralization in the central gyre region. Dotted lines delineate surface water (SW), CDW, and upper and lower layers of AABW. Graeme A. MacGilchrist et al. Sci Adv 2019;5:eaav6410 Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).