Enhanced North Pacific Subpolar Gyre Circulation Led to Hypoxia Events During Last Deglacial Warm Periods

Abstract Two episodes of expansion and strengthening of subsurface oxygen minimum zones (OMZ) associated with seafloor hypoxia occurred in the North Pacific during the Bolling‐Allerod (B/A) and early Holocene (EH) warm periods. The mechanisms driving these hypoxic events at high latitude, however, remain unclear. Here, we integrated multiple long‐chain alkenone temperature records () from the eastern and western margins of the North Pacific to infer the dynamics of the subpolar gyre (SPG). It was found that the mean temperature difference between NE and NW Pacific effectively reflects the variation in intensity of the SPG since the Last Glacial Maximum. During the B/A and EH warm periods, the northward shift of the westerlies led to strengthening of the SPG, and consequently, an increase in upwelling. The enhanced upwelling of nutrient‐rich waters highly likely resulted in increased biological productivity, and thus led to expansion of the OMZ underneath the SPG during the B/A and EH periods.