Intensification of the oxygen minimum zone in the northeast Pacific off Vancouver Island during the last deglaciation: Ventilation and/or export production?

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Abstract

[1] The oxygen minimum zone (OMZ) off Vancouver Island was more oxygen depleted relative to modern conditions during the Allerød (∼13.5 to 12.6 calendar kyr) and again from ∼11 to 10 kyr. The timing of OMZ intensification is similar to that seen throughout the North Pacific, although the onset appears to have been delayed by ∼1500 years off Vancouver Island. Radiocarbon dating of coeval benthic and planktonic foraminifera shows that between 16.0 and 12.6 kyr the age contrast between surface and intermediate waters (920 m depth) off Vancouver Island was similar to, or slightly less than, that today. There is no evidence of an increased age difference (i.e., decreased ventilation) during the deglaciation, particularly during the Allerød. However, sedimentary marine organic carbon concentration and mass accumulation rate increased substantially in the Allerød, suggesting that increased organic matter export was the principal cause of late Pleistocene OMZ intensification off Vancouver Island.

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