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Abstract:
The nitrate (NO3-) deposited in the polar ice sheet is an excellent archive of past solar activity; however, their reliability as a proxy for past solar activity is intensely debated owing to multiple sources and post-depositional processes. Several NO3- records from Antarctica show the signatures of solar events, whereas few do not offer any coincident nitrate peaks associated with these benchmark events. This issue can be addressed by evaluating selected ice core NO3- records from Antarctica against the instrumental records of past solar activity and reanalysing climate data. To resolve the issue of discontinuous signals and inconsistency in the solar activity signals extracted from various ice core records from Antarctica, we have investigated ten ice core nitrate records available across Antarctica for the typical interval during 1738-1990 CE. The statistical analysis of NO3- records reveals that solar activity is the dominant controlling factor of the total NO3- variability, followed by snow precipitation modulated by ENSO. In summary, the intensity of the solar cycle signal in the ice core NO3- the record is related to the threshold of sunspot numbers and is critical for detecting solar activity signals in the ice core NO3- records along with the snow accumulation rate. The key findings will improve our current understanding of the processes/factors that control ice core NO3- variability and its application as a solar proxy for past solar activity.
