Episodic release of CO from the high-latitude North Atlantic Ocean during the last 135 kyr.

Antarctic ice cores document glacial-interglacial and millennial-scale variability in atmospheric pCO over the past 800 kyr. The ocean, as the largest active carbon reservoir on this timescale, is thought to have played a dominant role in these pCO fluctuations, but it remains unclear how and where in the ocean CO was stored during glaciations and released during (de)glacial millennial-scale climate events. The evolution of surface ocean pCO in key locations can therefore provide important clues for understanding the ocean's role in Pleistocene carbon cycling. Here we present a 135-kyr record of shallow subsurface pCO and nutrient levels from the Norwegian Sea, an area of intense CO uptake from the atmosphere today. Our results suggest that the Norwegian Sea probably acted as a CO source towards the end of Heinrich stadials HS1, HS4 and HS11, and may have contributed to the increase in atmospheric pCO at these times.