Hjem
Geofysisk institutt

GFI/BCCR Seminar: Emergence and Development of the ‘100kyr World’

Hovedinnhold

Steve Barker (Cardiff University, UK):

Emergence and Development of the ‘100kyr World’

Abstract
The varying influence of Earth’s orbital geometry on climate is well documented, yet uncertainty over the precise interplay between orbital variations and the waxing and waning of continental ice sheets over tens of thousands of years continues to hinder our understanding of Earth’s climate system.

In particular, the emergence of approximately 100kyr glacial cyclicity across the Mid Pleistocene Transition (MPT, ~0.7 - 1Ma) gives rise to the so-called ‘100kyr problem’; why do such large changes in climate display dominant power ~100kyr while orbital forcing at this period (changes in the eccentricity of Earth’s orbit around the Sun) is so weak? Over recent decades it has become clear that the duration of Late Pleistocene glacial cycles is not precisely 100kyr but most likely multiples of 23 and 41kyr (the periods of precession and obliquity). For example glacial periods tend to terminate every 4 or 5 precession cycles, giving an average period of around 100kyr. Furthermore it is becoming apparent that millennial-scale changes in the ocean/atmosphere system (involving the so-called bipolar seesaw) may play an active role in the non-linear amplification of insolation forcing that has been required for terminating glacial periods since the MPT.

Here I will show the latest results from an ongoing project to produce a 1.7Myr record of sub-millennial-scale variability from the surface NE Atlantic Ocean. I will argue that the emergence of ‘100kyr periodicity’ was paralleled by the appearance of ‘seesaw-driven terminations’ and relate this to the increase in northward heat and moisture transport associated with a strengthening of the Nordic heat pump across the MPT.