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<p>Changes in the geometry of ocean meridional overturning circulation (MOC) are crucial in controlling past changes of climate and the carbon inventory of the atmosphere. However, the accurate timing and global correlation of short-term glacial-to-deglacial changes of MOC in different ocean basins still present a major challenge. The fine structure of jumps and plateaus in atmospheric and planktic radiocarbon (<span class="inline-formula">¹⁴C</span>) concentration reflects changes in atmospheric <span class="inline-formula">¹⁴C</span> production, ocean–atmosphere <span class="inline-formula">¹⁴C</span> exchange, and ocean mixing. Plateau boundaries in the atmospheric <span class="inline-formula">¹⁴C</span> record of Lake Suigetsu, now tied to Hulu Cave <span class="inline-formula">U∕Th</span> model ages instead of optical varve counts, provide a stratigraphic “rung ladder” of up to 30 age tie points from 29 to 10 cal ka for accurate dating of planktic oceanic <span class="inline-formula">¹⁴C</span> records. The age differences between contemporary planktic and atmospheric <span class="inline-formula">¹⁴C</span> plateaus record the global distribution of <span class="inline-formula">¹⁴C</span> reservoir ages for surface waters of the Last Glacial Maximum (LGM) and deglacial Heinrich Stadial 1 (HS-1), as documented in 19 and 20 planktic <span class="inline-formula">¹⁴C</span> records, respectively. Elevated and variable reservoir ages mark both upwelling regions and high-latitude sites covered by sea ice and/or meltwater. <span class="inline-formula">¹⁴C</span> ventilation ages of LGM deep waters reveal opposed geometries of Atlantic and Pacific MOC. Like 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. During early HS-1, <span class="inline-formula">¹⁴C</span> ventilation ages suggest a reversed MOC and <span class="inline-formula">∼1500</span>-year 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. High <span class="inline-formula">¹⁴C</span> ventilation ages of LGM deep waters reflect a major drawdown of carbon from the atmosphere. The subsequent major deglacial age drop reflects changes in MOC accompanied by massive carbon releases to the atmosphere as recorded in Antarctic ice cores. These new features of MOC and the carbon cycle provide detailed evidence in space and time to test and refine ocean models that, in part because of insufficient spatial model resolution and reference data, still poorly reproduce our data sets.</p>