Sulfur isotopes: the 1453 volcano was outside the tropics, near or upwind of Greenland

Burke et al. 2023 measured sulfur isotopes through the 1453 sulfate in the Tunu2013 Greenland core. The first sulfate to arrive has no mass-independent signal (delta-33S = 0) and low delta-34S: it travelled below the ozone layer, which requires a volcano close to or upwind of Greenland, the same pattern as Katmai (Alaska, 1912) and the 536 eruption. Only about 54 percent of the 1453 sulfate came through the high stratosphere, so the real stratospheric load was about half the ice-core estimate. Abbott et al. 2021 confirm the date by layer counting: an eruption in 1452 or early 1453. A loose end: some Antarctic cores show a small sulfate peak at the same time, which an eruption outside the tropics would not normally produce.