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New Study: Arctic Climate & Sea Ice Extent Related To Solar Activity

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The Hockey Schtick

A paper published by the Danish Meteorological Institute finds a remarkable correlation of Arctic sea ice observations over the past 500 years to “the solar cycle length, which is a measure of solar activity. A close correlation (R=0.67) of high significance (0.5 % probability of a chance occurrence) is found between the two patterns, suggesting a link from solar activity to the Arctic Ocean climate.”

The paper adds to several others demonstrating that Arctic sea ice extent and climate is controlled by natural variations in solar activity, ocean & atmospheric oscillations, winds & storm activity, not man-made CO2.

Solar Cycle Length [SCL] shown by dotted line, Koch sea ice extent index from observations in the Greenland Sea shown by solid line.

Multi-decadal variation of the East Greenland Sea-Ice Extent: AD 1500-2000

Knud Lassen and Peter Thejll

Abstract: The extent of ice in the North Atlantic varies in time with time scales stretching to centennial, and the cause of these variations is discussed. We consider the Koch ice index which describes the amount of ice sighted from Iceland, in the period 1150 to 1983 AD. This measure of ice extent is a non-linear and curtailed measure of the amount of ice in the Greenland Sea, but gives an overall view of the amounts of ice there through more than 800 years. The length of the series allows insight into the natural variability of ice extent and this understanding can be used to evaluate modern-day variations. Thus we find that the recently reported retreat of the ice in the Greenland Sea  may be related to the termination of the so-called Little Ice Age in the early twentieth century. We also look at the approximately 80 year variability of the Koch [sea ice] index and compare it to the similar periodicity found in the solar cycle length, which is a measure of solar activity. A close correlation (R=0.67) of high significance (0.5 % probability of a chance occurrence) is found between the two patterns, suggesting a link from solar activity to the Arctic Ocean climate. […]

Conclusion

In view of the large significance observed we suggest that the correlation of 0.67, between multi-decadal modes in the Koch ice index and the solar cycle length, is indicative of a relationship not due to chance.

The multi-decadal modes still represent only a small fraction of the total variance in the ice series, which illustrates that while the kind of solar activity characterised by the variable length of the solar cycle may cause some of the variability seen in the ice series, the majority is caused by other factors.

Whereas the multi-decal mode may be a result of varying solar activity, the cause of the slowly varying mode is not directly seen from the data presented here. Obviously, it must be due to a natural variation of the climate. A variation of similar shape may be recognised in the solar cycle length (Figure 5), but it has not been possible from the present data to deduce a correlation that is significant. Nevertheless, the similarity of the variation of the ice export through the Fram Strait and the smoothed variation of the solar cycle length shown in Figure 1.7 speaks in favour of the assumption that the solar cycle variation may include both natural modes. This conclusion is in accordance with the finding by Bond et al., 2001 (their Figure 2) that a persistent series of solar influenced millennial-scale variations, which include the Medieval Warm Period and the Little Ice Age, reflect a baseline of the centennial-scale cycles.

The ’low frequency oscillation’ that dominated the ice export through the Fram Strait as well as the extension of the sea-ice in the Greenland Sea and Davis Strait in the twentieth century may therefore be regarded as part of a pattern that has existed through at least four centuries. The pattern is a natural feature, related to varying solar activity. The considerations of the impact of natural sources of variability on arctic ice extent are of relevance for concerns that the current withdrawal of ice may entirely be due to human activity. Apparently, a considerable fraction of the current withdrawal could be a natural occurrence.

The Hockey Schtick, 17 July 2013