Marine core evidence for reduced deep water production during Termination II followed by a relatively stable substage 5e (Eemian)

Abstract

We present oxygen and carbon isotope records of benthic foraminifera from the glacial stage 6 through interglacial substage 5e (Eemian) sections of several cores from the subpolar North Atlantic. The cores range in water depth from 1451 to 2658 m. In one core, we generated estimates of sea surface temperature (SST) and of ice‐rafted detritus (IRD) delivery for all of stage 5. We reconstruct bathymeric profiles of δ13C for stage 6, Termination II, and three time slices of substage 5e. The δ13C profiles indicate that local deep water geometry during stage 6 was similar to that of the last glaciation, with glacial North Atlantic Intermediate Water (GNAIW) overlying deeper waters partially of southern origin. An anomalously large peak in IRD, coupled with planktonic δ18O evidence for iceberg melting immediately precedes Termination II and is otherwise similar to stage 2 and 3 Heinrich events. During the termination, low δ13C values are observed in cores near and above 2 km, providing evidence of reduced GNAIW production in association with deglacial melting. In the shallowest cores, low δ13C values persist into early substage 5e, indicating that the southward retreat of southern‐source waters was not completed until well after the beginning of the substage. In contrast to Termination I, SSTs remained cold until the end of the deglaciation; this may be why there is little evidence from marine and terrestrial sequences for a pronounced climate reversal on Termination II despite what is now clear evidence of a significant reduction in ocean ventilation. The faunal data suggest that SSTs during early 5e were about 7°C warmer than during the glaciation. SST rose several degrees from early to middle substage 5e, peaked in middle substage 5e at about 10°C above glacial values, and then gradually declined by about 5°C. These changes were linked to variations in water mass configuration, as interpreted from benthic δ13C evidence. Most of the evidence suggests that oscillations superimposed on the gradual SST trend were 1°–2°C, in contrast to the larger SST changes (3°–4°C) documented for substage 5d.