ScienceDaily (July 16, 2012) — The Atlantic Meridional Overturning Circulation (AMOC), driven by temperature and salinity gradients, is an important component of the climate system; it transfers an enormous amount of heat via ocean currents and atmospheric circulation to high northern latitudes and hence has bearing on climate in the region.
Previous paleoclimatic reconstructions indicate that the sub-Arctic may have been warmer by about 5 degrees Celcius (9 degrees Fahrenheit) with little summer sea ice cover during the Eemian, the penultimate interglacial centered around 125,000 years ago. Climate models favoring polar amplification use the Eemian as an analog of the present. In a new study, Bauch et al. compare reconstructed temperatures and water masses from two sediment cores that record the flow of meltwater in the subpolar and polar North Atlantic over the past 135,000 years. They do not find evidence of extreme warmth in the sub-Arctic during the Eemian interglacial period.
In fact, the Arctic may have been colder during the Eemian, with lower heat transfer from the North Atlantic. On the basis of their finding, the authors suggest that previous records may reflect other phenomena and caution against the use of the Eemian as an analog of the present. Their finding also challenges climate models that predict extreme warmth and ice-free conditions in the Arctic in response to greenhouse gas warming in the 21st century.
GEOPHYSICAL RESEARCH LETTERS, VOL. 39, L11604, 7 PP., 2012
Contrasting ocean changes between the subpolar and polar North Atlantic during the past 135 ka
- Reduced AMOC during the Eemian
- BA/YD-type warming/cooling in Termination 1 and 2
- Comparison of glacial inceptions reveals present climate status
Akademie der Wisssenschaften und der Literatur Mainz, Helmholtz-Zentrum für Ozeanforschung, Kiel, Germany
Helmholtz-Zentrum für Ozeanforschung, Kiel, Germany
Institute for Advanced Sustainability Studies, Potsdam, Germany