The climate is mild enough in North West Ireland for palm trees to grow because of the Atlantic meridional overturning circulation which transports heat from the Southern Hemisphere and the tropics to the North Atlantic. The photo below is being used as an illustration in a publication of the U.S. Geological Survey on the subject of rapid climate change. It is included as figure 1.7 (with permission) in chapter one (SAP 3.4.1) written by Peter Clark, Andrew Weaver, Ed Brook, Edward Cook, Tom Delworth, and Konrad Steffen. The photo was made on January 15, 2004 at Mullaghmore Head in County Sligo, Ireland.
A more recent
paper concerning the Atlantic meridonal overturning circulation
One of the authors had a copy of the full paper on a web page at
http://mgg.coas.oregonstate.edu/~andreas/pdf/M/marcott11pnas.pdf at the time of this writing.
Episodic iceberg-discharge events from the Hudson Strait Ice Stream (HSIS) of the Laurentide Ice Sheet, referred to as Heinrich events, are commonly attributed to internal ice-sheet instabilities, but their systematic occurrence at the culmination of a large reduction in the Atlantic meridional overturning circulation (AMOC) indicates a climate control. We report Mg/Ca data on benthic foraminifera from an intermediate-depth site in the northwest Atlantic and results from a climate-model simulation that reveal basin-wide subsurface warming at the same time as large reductions in the AMOC, with temperature increasing by approximately 2#°C over a 1-2 kyr interval prior to a Heinrich event. In simulations with an ocean model coupled to a thermodynamically active ice shelf, the increase in subsurface temperature increases basal melt rate under an ice shelf fronting the HSIS by a factor of approximately 6. By analogy with recent observations in Antarctica, the resulting ice-shelf loss and attendant HSIS acceleration would produce a Heinrich event.
We have some single subject photo index pages:
An interesting paper on the Atlantic meridonal overturning circulation:
Physical Sciences - Environmental Sciences:
* Matthias Hofmann
* and Stefan Rahmstorf
Tipping Elements in Earth Systems Special Feature: On the stability of the
Atlantic meridional overturning circulation
PNAS published online before print November 6, 2009,
PDF copy of the
paper on the stability of the Atlantic meridonal overturning circulation
is at http://academics.eckerd.edu/instructor/hastindw/MS1410-001_FA08/handouts/BrydenTHC05.pdf.
The Atlantic meridional overturning circulation (AMOC)â€”a system of ocean currents in the North Atlanticâ€”has a major impact on climate, yet its evolution during the industrial era is poorly known owing to a lack of direct current measurements. Here we provide evidence for a weakening of the AMOC by about 3â€‰Â±â€‰1 sverdrups (around 15 per cent) since the mid-twentieth century. This weakening is revealed by a characteristic spatial and seasonal sea-surface temperature â€˜fingerprintâ€™â€”consisting of a pattern of cooling in the subpolar Atlantic Ocean and warming in the Gulf Stream regionâ€”and is calibrated through an ensemble of model simulations from the CMIP5 project. We find this fingerprint both in a high-resolution climate model in response to increasing atmospheric carbon dioxide concentrations, and in the temperature trends observed since the late nineteenth century. The pattern can be explained by a slowdown in the AMOC and reduced northward heat transport, as well as an associated northward shift of the Gulf Stream. Comparisons with recent direct measurements from the RAPID project and several other studies provide a consistent depiction of record-low AMOC values in recent years.
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