Dominant Northern Hemisphere climate control over millennial-scale glacial sea-level variability

Abstract

Based on a radiocarbon and paleomagnetically dated sediment record from the northern Red Sea and the exceptional sensitivity of the regional changes in the oxygen isotope composition of sea water to the sea-level-dependent water exchange with the Indian Ocean, we provide a new global sea-level reconstruction spanning the last glacial period. The sea-level record has been extracted from the temperature-corrected benthic stable oxygen isotopes using coral-based sea-level data as constraints for the sea-level/oxygen isotope relationship. Although, the general features of this millennial-scale sea-level records have strong similarities to the rather symmetric and gradual Southern Hemisphere climate patterns, we observe, in constrast to previous findings, pronounced sea level rises of up to 25 m to generally correspond with Northern Hemisphere warmings as recorded in Greenland ice-core interstadial intervals whereas sea-level lowstands mostly occur during cold phases. Corroborated by CLIMBER-2 model results, the close connection of millennial-scale sealevel changes to Northern Hemisphere temperature variations indicates a primary climatic control on the mass balance of the major Northern Hemisphere ice sheets and does not require a considerable Antarctic contribution. r

Differences between the last two glacial maxima and implications for ice-sheet, δ18O, and sea-level reconstructions

“…2b). However, sparse LGM data from bulk carbonate are supported by other Red Sea records that indicate a 5e5.5‰ change in foraminiferal d 18 O between the LGM and present (Arz et al, 2003(Arz et al, , 2007, compared with 4‰ between the PGM and present (Rohling et al, 2009). Moreover, the aplanktonic LGM Red Sea conditions offer strong independent evidence that LGM sea level was lower than in the PGM.…”

Convincing evidence for rapid ice sheet growth during the last glacial period

“…1) strongly couple Red Sea oxygen isotope ratios with sea level. This is best exemplified by the full glacial-interglacial range of change in stable oxygen isotope ratios in water of 4.5-5‰ (allowing for a 4°C glacial to interglacial temperature range (Arz et al, 2007)), compared to ~1-1.2‰ in the open ocean (Thunell et al, 1988;Hemleben et al, 1996;Rohling et al, 1998;Fenton et al, 2000;Siddall et al, 2003;Arz et al, 2003). Siddall et al (2003) used a three-layer hydraulic model to calculate water-mass exchange at the sill (Siddall et al, 2002), (Werner and Lange, 1975;Rohling et al, 1998;Fenton et al, 2000;Siddall et al, 2002;2004 coupled to a model of oxygen isotope fractionation in an evaporative basin (Rohling, 1999).…”

“…Recently, Arz et al (2007) used temperature estimates from coccolithophore-based long-chain alkenone unsaturation ratios, in combination with benthic foraminifer-based oxygen isotope records from a core in the northernmost Red Sea, to estimate a seawater oxygen isotope record for MIS 3. This record was then empirically scaled to sea level using coral-based sea level estimates.…”

“…Benthic isotopes in the Red Sea may respond less quickly to varying sea level than those in planktic organisms and may, therefore, smooth out rapid variations in sea level. The Arz et al (2007) reconstruction was further smoothed using a 5-point running mean.…”

“…As the underlying mechanism of sea level forcing on Red Sea oxygen isotope ratios is the same for both the approach of Arz et al (2007) and Siddall et al (2003) there should be strong similarities between the different reconstructions. To facilitate comparison, Figure 2 plots all three records after transformation to a common (arbitrary) age scale.…”