By G.A. MacGilchrist, H.L. Johnson, C. Lique, D. Marshall

Published in Geophysical Res. Lets.

Plain Language Summary

Water that leaves the ocean’s surface boundary layer — where water is in direct contact with the overlying atmosphere — to be transported into the subsurface, is said to be “ventilated” (the name arising from the abundance of oxygen in newly ventilated water). The ventilation process, which carries implications for the ocean storage of climate‐relevant substances such as carbon dioxide, occurs only at certain times and under certain conditions. In describing a mechanism for the selective nature of ventilation over the seasonal cycle, Henry Stommel imagined a Demon sitting at the base of the surface boundary layer, granting access only to parcels of water that meet certain characteristics (namely their speed of “escape”). Thus, “Stommel’s Demon” was born. Here, we investigate this same process as it operates in more northerly regions and on longer timescales. In so doing we give birth to a new “interannual Demon”, and describe its characteristics.