Climatic and insolation control on the high-resolution total air content in the NGRIP ice core

• Main Authors: Eicher, O., Baumgartner, M., Schilt, A., Schmitt, J., Schwander, J., Stocker, T. F., Fischer, H.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2016
• Subjects: 530 Physics; Antarctic; The Antarctic; Greenland; Tac; Antarc*; Dansgaard-Oeschger events; Greenland ice core; Greenland Ice core Project; ice core; Ice Sheet; NGRIP; North Greenland; North Greenland Ice Core Project
• Online Access: https://boris.unibe.ch/89328/1/eicher16clp.pdf; https://boris.unibe.ch/89328/

Because the total air content (TAC) of polar ice is directly affected by the atmospheric pressure, its record in polar ice cores was considered as a proxy for past ice sheet elevation changes. However the Antarctic ice core TAC record is known to also contain an insolation signature, although the underlying physical mechanisms are still a matter of debate. Here we present a high-resolution TAC record over the whole North Greenland Ice Core Project ice core, covering the last 120 000 years, which independently supports an insolation signature in Greenland. Wavelet analysis reveals a clear precession and obliquity signal similar to previous findings on Antarctic TAC, with different insolation history. In our high-resolution record we also find a decrease of 3–5% (3–4.2mLkg⁻¹) in TAC as a response to Dansgaard-Oeschger-Events (DO-events). TAC starts to decrease in parallel to increasing Greenland surface temperature and slightly before CH₄ reacts to the warming, but also shows a two-step decline that lasts for several centuries into the warm phase/interstadial. The TAC response is larger than expected considering only local temperature and atmospheric pressure as a driver, pointing to transient firnification response caused by the accumulation-induced increase in the load on the firn at bubble close-off, while temperature changes deeper in the firn are still small.