Benthic δ18O records in the North Atlantic over the last glacial period (60-10 kyr):: Evidence for brine formation

Four high-resolution benthic isotope records from North Atlantic and south Norwegian Sea cores are compared for the past 60 kyr. The benthic records show light delta(18)O peaks simultaneously to or following the Heinrich events. The amplitude of these light peaks varies between 1 parts per thousand for the most northern core ENAM93-21 and 0.35 parts per thousand for the deep North Atlantic cores. The high delta(18)O gradient between the North Atlantic cores and the Pacific core V19-30 suggests a regional influence of delta(18)O-depleted meltwater to deeper depth during periods of iceberg discharges. The most likely process for transferring delta(18)O-depleted meltwater to depth is sea ice formation induced by brine formation. During Heinrich events 4 and 3 this mecanism was of major importance (compared to open ocean convection) in the southern Norwegian Sea and at the northern boundaries of the Atlantic, leading to intermediate to deep water formation. Other delta(18)O excursions appearing in all the records point to the contribution of both brine formation and global changes in the delta(18)O of seawater associated with the Heinrich event periods.