Benthic δ18O evidence for the transfer of Common Era surface temperature anomalies via North Atlantic Deep Water

The North Atlantic plays a key role in regulating overturning circulation and the global heat budget, as it is the site of North Atlantic Deep Water (NADW) formation and over 50% of oceanic heat uptake. Recent work suggests that accurate estimates of ocean heat uptake due to anthropogenic warming require knowledge of the deep ocean response to pre-Industrial temperature variability (Gebbie and Huybers, 2019). To investigate how surface temperature variations during the Common Era influenced the ocean interior, we examine how Iceland-Scotland Overflow Water (ISOW) and Labrador Sea Water (LSW), two components of NADW, responded to well-documented and widespread North Atlantic surface trends over the past 2000 years, namely the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA). Here, we present records of stable oxygen isotopes of benthic foraminifera from two sites, EN539-14MC/15GGC, located in the pathway of ISOW, and CH07-98-22MC, located in the subtropics within the LSW density class. Assuming benthic δ¹⁸O variability at these sites is dominated by temperature, we compare the amplitude of the MCA-LIA transition to cooling predicted at each site by an inversion of hydrographic and paleoceanographic data (Gebbie and Huybers, 2019). Preliminary data suggest MCA-LIA cooling, although with a timing different from the model.