The new Kr-86 excess ice core proxy for synoptic activity: West Antarctic storminess possibly linked to Intertropical Convergence Zone (ITCZ) movement through the last deglaciation

• Published in: Climate of the past Vol. 19; no. 3; pp. 579 - 606
• Main Authors: Buizert, Christo, Shackleton, Sarah, Severinghaus, Jeffrey P, Roberts, William H. G, Seltzer, Alan, Bereiter, Bernhard, Kawamura, Kenji, Baggenstos, Daniel, Orsi, Anaïs J, Oyabu, Ikumi, Birner, Benjamin, Morgan, Jacob D, Brook, Edward J, Etheridge, David M, Thornton, David, Bertler, Nancy, Pyne, Rebecca L, Mulvaney, Robert, Mosley-Thompson, Ellen, Neff, Peter D, Petrenko, Vasilii V
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 15.03.2023; European Geosciences Union (EGU); Copernicus Publications
• Subjects: Air transport; Air transportation; Aircraft; Analysis; Antarctic ice sheet; Antarctic zone; Atmosphere; Atmospheric circulation; Atmospheric dynamics; Atmospheric models; Climate; Climate change; Convergence; Convergence zones; Cores; Corrections; Correlation; Deglaciation; Dynamic meteorology; El Nino; El Nino phenomena; El Nino-Southern Oscillation event; Empirical analysis; Equilibrium; Firn; Fractionation; Gas sampling; Gases; Glacial periods; Glaciation; Gravity; Holocene; Holocene ice; Ice; Ice cores; Ice sheets; Intertropical convergence zone; Isotopes; Krypton; Last Glacial Maximum; Meltwater; Monsoon intensity; Ocean circulation; Opal; Physics; Polar environments; Pressure; Pressure changes; Proxy; Records; Sciences of the Universe; Southern Hemisphere; Southern Oscillation; Surface pressure; Time series; Upwelling; Variability; Vortices; Wind-driven upwelling; Younger Dryas; Antarctica
• ISSN: 1814-9332; 1814-9324; 1814-9332
• DOI: 10.5194/cp-19-579-2023

Here we present a newly developed ice core gas-phase proxy that directly samples a component of the large-scale atmospheric circulation: synoptic-scale pressure variability. Surface pressure changes weakly disrupt gravitational isotopic settling in the firn layer, which is recorded in krypton-86 excess (.sup.86 Kr.sub.xs). The .sup.86 Kr.sub.xs may therefore reflect the time-averaged synoptic pressure variability over several years (site "storminess"), but it likely cannot record individual synoptic events as ice core gas samples typically average over several years. We validate .sup.86 Kr.sub.xs using late Holocene ice samples from 11 Antarctic ice cores and 1 Greenland ice core that collectively represent a wide range of surface pressure variability in the modern climate. We find a strong spatial correlation (r=-0.94, p<0.01) between site average .sup.86 Kr.sub.xs and time-averaged synoptic variability from reanalysis data. The main uncertainties in the analysis are the corrections for gas loss and thermal fractionation and the relatively large scatter in the data. Limited scientific understanding of the firn physics and potential biases of .sup.86 Kr.sub.xs require caution in interpreting this proxy at present. We show that Antarctic .sup.86 Kr.sub.xs appears to be linked to the position of the Southern Hemisphere eddy-driven subpolar jet (SPJ), with a southern position enhancing pressure variability.