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Millennial-Scale Cycling of Climate in Disko Bugt, West Greenland

Reference
Perner, K., Moros, M., Lloyd, J.M., Kuijpers, A., Telford, R.J. and Harff, J. 2011. Centennial scale benthic forminiferal record of late Holocene oceanographic variability in Disko Bugt, West Greenland. Quaternary Science Reviews 30: 2815-2816.
Based on the identification and quantification of various foraminiferal species found in a sediment core extracted from the bottom of a deep-water trough (Egedesminde Dyb) in the southwestern Disko Bugt of West Greenland at coordinates of ~68°38'N, 53°49'W, Perner et al. (2011) derived a 3600-year temperature history of the West Greenland Current at that location.

The six researchers -- hailing from Denmark, Germany, Norway, Poland and the United Kingdom -- say that their new high-resolution benthic foraminiferal record from Disko Bugt "documents a marked long-term cooling trend over the last 3.6 ka BP," but they state that superimposed on this longer-term late Holocene cooling trend, there is evidence of millennial to centennial scale variability. This variability begins with what they describe as "a pronounced cooling event" at c. 2.5 ka BP, after which "a warm phase in bottom waters is recorded at c. 1.8 ka BP, which corresponds to the 'Roman Warm Period' and is seen to represent the warmest bottom water conditions recorded in Disko Bugt during the last 3.6 ka BP." This unique warm period was in turn followed by a cooler period (which would obviously be the Dark Ages Cold Period), after which they identify a warming of the subsurface waters during the 'Medieval Climate Anomaly'," which was followed (from 0.9 ka BP) by "pervasive and even harsher environmental conditions" that ultimately culminate at 0.3 ka BP in what they say is the Little Ice Age, and from which the region has yet to recover to Medieval Warm Period conditions.

The unique warmth of the Roman Warm Period at Disko Bugt is also supported, in the words of Perner et al., by the "relatively high and stable air temperatures over the Greenland ice cap (Alley et al., 1999) and is associated with enhanced meltwater production as demonstrated in sediment core records from Ammarilik fjord, West Greenland (e.g. Moller et al., 2006)," as well as by "findings from Jennings et al. (2002), who report a warming within the East Greenland Current on the East Greenland shelf from c. 2.1 to 1.4 ka BP." Thus, for this particular part of the planet (and for most of the rest of the world as well), it can be seen that multi-century cycling of climate between relatively warmer and cooler conditions is quite normal. And it can thus be appreciated that 20th-century global warming was only to be expected to occur when it did, and that it could reasonably be expected that the region may warm even more before cooling again, for it still has a ways to go to equal the warmth of the Roman Warm Period or even the Medieval Warm Period, which in many locations was also warmer than it is currently.

Additional References
Alley, R.B., Agustsdottir, A.M. and Fawcett, P.J. 1999. Ice-core evidence of late-Holocene reduction in North Atlantic Ocean heat transport. Geophysical Monograph 112: 301-312.

Jennings, A., Knudsen, K.L., Hald, M., Hansen, C.V. and Andrews, J.T. 2002. A mid-Holocene shift in Arctic sea-ice variability on the East Greenland shelf. The Holocene 12: 49-58.

Moller, H.S., Jensen, K.G., Kuijpers, A., Aagaard-Sorensen, S., Seidenkrantz, M.-S., Prins, M., Endler, R. and Mikkelsen, N. 2006. Late-Holocene environment and climatic changes in Ameralik Fjord, southwest Greenland: evidence from the sedimentary record. The Holocene 16: 685-695.

Archived 15 November 2011