Changes in the geometry of ocean Meridional Overturning Circulation (MOC) are crucial in controlling changes of climate and the carbon inventory of the atmosphere. However, the precise timing and global correlation of short-term glacial-to-deglacial changes of MOC in different ocean basins still present a major challenge. A possible solution is offered by the fine structure of jumps and plateaus in the record of radio-carbon (<sup>14</sup>C) concentration of the atmosphere and surface ocean that reflects changes in atmospheric <sup>14</sup>C production as well as in the <sup>14</sup>C exchange between air and sea and within the ocean. Boundaries of atmospheric <sup>14</sup>C plateaus in the <sup>14</sup>C record of Lake Suigetsu, now tied to Hulu U/Th model-ages instead of optical varve counts, provide a stratigraphic "rung ladder" of ~30 age tie points from 29 to 10 ka for correlation with and dating of planktic oceanic <sup>14</sup>C records. The age difference between contemporary planktic and atmospheric <sup>14</sup>C plateaus gives an estimate of the global distribution of <sup>14</sup>C reservoir ages for surface waters of the Last Glacial Maximum (LGM) and deglacial Heinrich Stadial 1 (HS-1), as shown by 19 planktic <sup>14</sup>C records. Clearly elevated and variable reservoir ages mark both high-latitude sites covered by sea ice and/or meltwater and upwelling regions. <sup>14</sup>C ventilation ages of LGM deep waters reveal opposed geometries of Atlantic and Pacific MOC. Similar to today, Atlantic deep-water formation went along with an estuarine inflow of old abyssal waters from the Southern Ocean up to the northern North Pacific and an outflow of upper deep waters. Vice versa, <sup>14</sup>C ventilation ages suggest a reversed MOC during early HS-1 and a ~1500 year long flushing of the deep North Pacific up to the South China Sea, when estuarine circulation geometry marked the North Atlantic, gradually starting near 19 ka. Elevated <sup>14</sup>C ventilation ages of LGM deep waters reflect a major drawdown of carbon from the atmosphere. Inversely, the subsequent massive age drop and change in MOC induced two major events of carbon release to the atmosphere as recorded in Antarctic ice cores, shifts that highlight the significance of ocean MOC for atmospheric CO<sub>2</sub> and its <sup>14</sup>C inventory. These new features of MOC and the carbon cycle offer a challenge to model simulations that, in part because of insufficient spatial model resolution and reference data for testing the model results, still poorly reproduce them.