Evidence of the solar Gleissberg cycle in the nitrate concentration in polar ice

• We found the century-type variation in Greenland nitrate during AD 1576–1970.
• We found the century-type variation in Antarctic nitrate during AD 1576–1970.
• We obtained evidence of solar origin of the revealed century-scale variations.

Two sets of nitrate (NO3−) concentration data, obtained from Central Greenland and East Antarctic (Dronning Maud Land) ice cores, were analyzed statistically. Distinct century-scale (50–150 yr) variability was revealed in both data sets during AD 1576–1990. It was found that century-type variation in Greenland and Antarctic nitrate correlates fairly significantly with the corresponding Gleissberg cycle: (a) in sunspot number over 1700–1970 AD; (b) in 10Be concentration in Central and South Greenland over 1576–1970 AD. Thus, presence of century-scale relationship between polar nitrate and solar activity was confirmed over the last 4 centuries. That proves that NO3− concentration in polar ice caps could serve as indicator of long-term solar variability.