Modern solar maximum forced late twentieth century Greenland cooling

Abstract

The abrupt Northern Hemispheric warming at the end of the twentieth century has been attributed to an enhanced greenhouse effect. Yet Greenland and surrounding subpolar North Atlantic remained anomalously cold in 1970s to early 1990s. Here we reconstructed robust Greenland temperature records (North Greenland Ice Core Project and Greenland Ice Sheet Project 2) over the past 2100 years using argon and nitrogen isotopes in air trapped within ice cores and show that this cold anomaly was part of a recursive pattern of antiphase Greenland temperature responses to solar variability with a possible multidecadal lag. We hypothesize that high solar activity during the modern solar maximum (approximately 1950s–1980s) resulted in a cooling over Greenland and surrounding subpolar North Atlantic through the slowdown of Atlantic Meridional Overturning Circulation with atmospheric feedback processes.

Post-bubble close-off fractionation of gases in polar firn and ice cores: effects of accumulation rate on permeation through overloading pressure

“…GISP2 and NGRIP (North Greenland Ice Core Project) data have been published earlier (Kobashi et al, 2008b(Kobashi et al, , 2015, and Dome Fuji data are new. Importantly, storage histories of these cores (i.e., temperatures) are known and methods for measuring δAr/N 2 are all comparable.…”

“…For NGRIP, sample resolution is about 10 years throughout the past 2100 years (Kobashi et al, 2015). Both GISP2 and NGRIP have similar annual average temperatures of approximately −30 • C (Table 1).…”

“…The ice samples were then cut and moved to the Scripps Institution of Oceanography, where δAr/N 2 was measured in 2005 (Kobashi et al, 2008b). On the other hand, the NGRIP2 ice cores (one of the two NGRIP ice cores; 64.6 m-445.2 m) (Kobashi et al, 2015). Accumulation rates Cuffey and Clow, 1997;Gkinis et al, 2014) Kipfstuhl, personal communication, 2015).…”

“…Dome Fuji data have neither precise temperatures nor accumulation rates over the past 2100 years. The annual resolution accumulation rate data were smoothed with 21-year RMs to correspond to gas diffusion and the bubble close-off process in the firn (Kobashi et al, 2015). A spline fit (Enting, 1987) was applied to gas data (e.g., δAr/N 2 ) with a 21-year cut-off period to be consistent with 21 RMs of other parameters and used for the following analyses to investigate signals longer than the decadal timescale.…”

“…The gas age uncertainties relative to ice age were estimated as ∼ 10 % of the estimated gas age-ice age difference (Goujon et al, 2003). To investigate the δAr/N 2 fractionation, we used reconstructed temperature records from argon and nitrogen isotopes in the trapped air within the GISP2 ice core for the past 4000 years (Kobashi et al, 2011) and within NGRIP for the past 2100 years (Kobashi et al, 2015) and layer-counted accumulation rate data for the Holocene Cuffey and Clow, 1997;Gkinis et al, 2014). Dome Fuji data have neither precise temperatures nor accumulation rates over the past 2100 years.…”