Project 6:
Constraining the state and variability of the paleo-Atlantic
We have developed high quality geochemical and sedimentological records examining past variability in the deep circulation of the North Atlantic. Our work using traditional foraminiferal oxygen and carbon stable isotope analysis has provided vital constraints on past circulation changes that are used as a benchmark for changes in the northern North Atlantic during the end of the last Ice Age. Moreover, by applying newer proxies (i.e. benthic foraminiferal Mg/Ca and radiocarbon measurements) at high resolution to this much studied time interval, we have shown that the circulation of the North Atlantic was more variable and complex than previously expected. David & Alice are taking these concepts further and are exploring the temporal and spatial complexity of the Younger Dryas and its impact on the circum-North Atlantic cryosphere, using high-resolution marine inorganic and organic geochemical proxies, faunal assemblage analysis, and terrestrial archives. Additionally, by applying benthic foraminiferal Mg/Ca ratios, radiocarbon measurements and novel clumped isotope paleothermometry, we were able to explore the characteristics of the glacial deep Arctic Mediterranean and reveal that, following a stagnated glacial state, it likely released heat during the deglaciation that may have helped melt surrounding sea-ice and marine terminating glaciers. This work presented a fundamentally different view on the past circulation of this climatically sensitive region of the Earth.
Our cutting-edge research using paired Mg/Ca-δ18O analysis of multiple species of planktonic foraminifera also enabled us to demonstrate large amplitude Holocene variability in the temperature and salinity of the subpolar North Atlantic. This work was the first paleo study to draw attention to the importance of subpolar gyre (SPG) dynamics in millennial-scale climate change, including the suggestion of a climate stabilizing feedback mechanism during the Holocene ; the role of the SPG in past North Atlantic circulation changes is now a widely recognized mechanism. Follow-up work to examine centennial scale variability during the late Holocene which revealed how solar forcing caused coupled changes in atmosphere and ocean circulation.