Past Rates of Sea Level Change

Fig. 2: Comparison of oxygen isotope ratios of the benthic foraminifera B. dilatata (c) and C. wuellerstorfi (d) (Hüls, 2000) from sediment cores ODP 1078C (11°55’ S, 13°24’ E; 426 m water depth) and M35003-4 (12°05’ N, 61°15’ W; 1299 m water depth), respectively, indicating tropical Atlantic intermediate-depth temperatures, with (a) oxygen isotopes from the GISP2 ice core displaying air temperatures over Greenland, and (b) atmospheric radiocarbon from sediments of Lake Suigetsu, Japan (Kitagawa et al. 2000; adapted from Clark et al., 2002). 14C AMS control points for ODP 1078C and M35003-4 are denoted by triangles above the respective record. H1 and YD denote Heinrich event H1and the Younger Dryas period, respectively. The record of ΔCatm (b) is a function of the production rate of 14C in the upper atmosphere and the sizes of and exchange rates between the major carbon reservoirs. North Atlantic Deep Water (NADW) is presently the major source of 14C to the deep sea, and changes in the strength of this water mass probably dominate the variations in ΔCatm. Positive anomalies in the ΔCatm record hence largely refl ect reduction of NADW production and thermohaline overturning (Clark et al., 2002).