Differences in the rates and character of the last two glacial terminations - Ed Gasson (Bristol)

Compared with the intensely studied interval of the last glacial maximum and termination, significantly less attention has been given to the preceding glacial period and Termination 2. This is perhaps understandable as the Greenland ice cores do not stretch this far back in time and the terrestrial record of the ice sheets has in part been lost during the subsequent glacial period. However, there are many questions remaining about how these two glacial intervals differed and whether this was important in driving some of the differences between the last interglacial and our current interglacial. In this talk I’ll focus on two aspects of the penultimate glacial and highlight some of the contrasts with the most recent glacial period. 

The first is evidence for an Arctic ice shelf seen in extensive ice scouring on the Lomonosov Ridge in the central Arctic Ocean in water depths exceeding a kilometer. I’ll present modelling work that supports the interpretation that these features were caused by an ice shelf that extended across the entire Arctic Basin and discuss what significance an ice shelf may have had to the glacial Earth system. I’ll also discuss the dating of these features and why such a thick ice shelf may have formed during certain glacial stages and not others.

The second half of the talk will focus on a new speleothem record from northern Spain which records the meltwater-driven d18O anomaly in the eastern North Atlantic and provides an absolutely dated chronology (U/Th) during the penultimate glacial and Termination 2. The character of which differs dramatically from a record for Termination 1 recovered from speleothems at the same site. I’ll discuss some possible reasons for the differences between the two glacial terminations recorded at this site.