Due to time constraints, what follows is a shortened version of the original German blog article.
Danish Chinese scientists discover important relationship: Arctic sea ice development of the last 5000 years is controlled by solar activity
By Fritz Vahrenholt and Sebastian Lüning
(Translated/edited by P Gosselin)
Satellites began systematically measuring sea ice about 35 years ago. Such a data series is much too short to allow conclusions to be drawn concerning long-term trends. Thus it is necessary to use geological studies to trace back sea ice development far into the past. In October 2010 we reported on such a study and found that Baltic sea ice cover over the last 500 years has been coupled with solar activity. In October 2013, we also wrote another blog article on the subject (see our blog article “Arctic sea ice melted and grew in sync with the sun over the past 500 years“).
In June 2014 in the journal Palaeogeography, Palaeoclimatology, Palaeoecology, a Danish-Chinese team published a paper led by Longbin Sha. They reconstructed sea ice over the past 500 years at a bay located in Western Greenland The result in shown in Figure 1 and shows that sea ice was in sync with solar activity. The authors also found that fluctuations in solar activity were an important factor of influence for changes in sea ice over the last 5000 years. What follows is the abstract of the paper:
Relatively warm conditions with a strong influence of the Irminger Current (IC) were indicated for the early part of the record (~ 5000–3860 cal. yr BP), corresponding in time to the latest part of the Holocene Thermal Maximum. Between 3860 and 1510 cal. yr BP, April SIC oscillated around the mean value (55%) and during the time interval 1510–1120 cal. yr BP and after 650 cal. yr BP was above the mean, indicating more extensive sea-ice cover in Disko Bugt. Agreement between reconstructed April SIC and changes in the diatom species suggests that the sea-ice condition in Disko Bugt was strongly influenced by variations in the relative strength of two components of the West Greenland Current, i.e. the cold East Greenland Current and the relatively warm IC. Further analysis of the reconstructed SIC record suggests that solar radiation may be an important forcing mechanism behind the historic sea-ice changes.”
Figure 1: Sea ice development of Western Greenland (bottom chart). Low peaks indicated in gray show sea ice increase while high peaks show reduced sea ice. The upper curve depicts solar activity. Source: Sha et al. 2014.
The scale shows that solar activity was the primary driving factor over centuries, while ocean cycles played an important role on a decadal scale. In January 2014 a Norwegian-German-US research team published a paper on this in the Geophysical Research Letters. The scientists found a clear natural rhythm of 60-90 years where the Arctic sea ice grew and shrank. The research showed that the sea ice cycles apparently were driven by the Atlantic Multidecadal Oscillation (AMO). As a result the authors also believe that the sea ice will grow once again in the years and decades, (see Figure 2).
Figure 2: AMO. Source: Wikipedia.
The following is the abstract of the study:
A signal of persistent Atlantic multidecadal variability in Arctic sea ice
Satellite data suggest an Arctic sea ice-climate system in rapid transformation, yet its long-term natural modes of variability are poorly known. Here we integrate and synthesize a set of multicentury historical records of Atlantic Arctic sea ice, supplemented with high-resolution paleoproxy records, each reflecting primarily winter/spring sea ice conditions. We establish a signal of pervasive and persistent multidecadal (~60–90 year) fluctuations that is most pronounced in the Greenland Sea and weakens further away. Covariability between sea ice and Atlantic multidecadal variability as represented by the Atlantic Multidecadal Oscillation (AMO) index is evident during the instrumental record, including an abrupt change at the onset of the early twentieth century warming. Similar covariability through previous centuries is evident from comparison of the longest historical sea ice records and paleoproxy reconstructions of sea ice and the AMO. This observational evidence supports recent modeling studies that have suggested that Arctic sea ice is intrinsically linked to Atlantic multidecadal variability. This may have implications for understanding the recent negative trend in Arctic winter sea ice extent, although because the losses have been greater in summer, other processes and feedbacks are also important.”
In 2014 Paul Homewood wrote about this at WUWT. Homewood also sees cooling for the Arctic over the coming 30 years due to the AMO:
All these stations, ranging from western Greenland to Siberia, show essentially the same pattern, a warm period around 1940, comparable to now, and a much colder interlude in the 1960’s and 70’s. And, of course, these all closely follow the ups and downs of the AMO. There seems little doubt that the Arctic will be in for another cold period during the next 30 years or so, and that, as Judith Curry indicates, we will see a long term recovery of Arctic ice extent.”
For more information visit Tony Brown at WUWT.