Preprints
https://doi.org/10.5194/egusphere-2024-1003
https://doi.org/10.5194/egusphere-2024-1003
24 May 2024
 | 24 May 2024

Shifts in Greenland interannual climate variability lead Dansgaard-Oeschger abrupt warming by hundreds of years

Chloe A. Brashear, Tyler R. Jones, Valerie Morris, Bruce H. Vaughn, William H. G. Roberts, William B. Skorski, Abigail G. Hughes, Richard Nunn, Sune Olander Rasmussen, Kurt M. Cuffey, Bo M. Vinther, Todd Sowers, Christo Buizert, Vasileios Gkinis, Christian Holme, Mari F. Jensen, Sofia E. Kjellman, Petra M. Langebroek, Florian Mekhaldi, Kevin S. Rozmiarek, Jonathan W. Rheinlænder, Margit Simon, Giulia Sinnl, Silje Smith-Johnsen, and James W. C. White

Abstract. During the Last Glacial Period (LGP), Greenland experienced approximately thirty abrupt warming phases, known as Dansgaard-Oeschger (D-O) Events, followed by cooling back to baseline glacial conditions. Studies of mean climate change across warming transitions reveal indistinguishable phase-offsets between shifts in temperature, dust, sea salt, accumulation and moisture source, thus preventing a comprehensive understanding of the “anatomy” of D-O cycles (Capron et al,. 2021). One aspect of abrupt change that has not been systematically assessed is how high-frequency, interannual-scale climatic variability surrounding mean temperature changes across D-O transitions. Here, we utilize the EGRIP ice core high-resolution water isotope record, a proxy for temperature and atmospheric circulation, to quantify the amplitude of 7–15 year isotopic variability for D-O events 2–13, the Younger Dryas and the Bølling-Allerød. On average, cold stadial periods consistently exhibit greater variability than warm interstadial periods. Most notably, we often find that reductions in the amplitude of the 7–15 year band led abrupt D-O warmings by hundreds of years. Such a large phase offset between two climate parameters in a Greenland ice core has never been documented for D-O cycles. However, similar centennial lead times have been found in proxies of Norwegian Sea ice cover relative to abrupt Greenland warming (Sadatzki et al., 2020). Using HadCM3, a fully coupled general circulation model, we assess the effects of sea ice on 7–15 year temperature variability at EGRIP. For a range of stadial and interstadial conditions, we find a strong relationship in line with our observations between colder simulated mean temperature and enhanced temperature variability at the EGRIP location. We also find a robust correlation between year-to-year North Atlantic sea-ice fluctuations and the strength of interannual-scale temperature variability at EGRIP. Thus, both paleoclimate proxy evidence and model simulations suggest that sea ice plays a substantial role in high-frequency climate variability prior to D-O warming. This provides a clue about the anatomy of D-O Events and should be the target of future sea-ice model studies.

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Chloe A. Brashear, Tyler R. Jones, Valerie Morris, Bruce H. Vaughn, William H. G. Roberts, William B. Skorski, Abigail G. Hughes, Richard Nunn, Sune Olander Rasmussen, Kurt M. Cuffey, Bo M. Vinther, Todd Sowers, Christo Buizert, Vasileios Gkinis, Christian Holme, Mari F. Jensen, Sofia E. Kjellman, Petra M. Langebroek, Florian Mekhaldi, Kevin S. Rozmiarek, Jonathan W. Rheinlænder, Margit Simon, Giulia Sinnl, Silje Smith-Johnsen, and James W. C. White

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  • RC1: 'Comment on egusphere-2024-1003', Anonymous Referee #1, 08 Jul 2024
  • RC2: 'Review of egusphere-2024-1003', Anonymous Referee #2, 09 Jul 2024
Chloe A. Brashear, Tyler R. Jones, Valerie Morris, Bruce H. Vaughn, William H. G. Roberts, William B. Skorski, Abigail G. Hughes, Richard Nunn, Sune Olander Rasmussen, Kurt M. Cuffey, Bo M. Vinther, Todd Sowers, Christo Buizert, Vasileios Gkinis, Christian Holme, Mari F. Jensen, Sofia E. Kjellman, Petra M. Langebroek, Florian Mekhaldi, Kevin S. Rozmiarek, Jonathan W. Rheinlænder, Margit Simon, Giulia Sinnl, Silje Smith-Johnsen, and James W. C. White
Chloe A. Brashear, Tyler R. Jones, Valerie Morris, Bruce H. Vaughn, William H. G. Roberts, William B. Skorski, Abigail G. Hughes, Richard Nunn, Sune Olander Rasmussen, Kurt M. Cuffey, Bo M. Vinther, Todd Sowers, Christo Buizert, Vasileios Gkinis, Christian Holme, Mari F. Jensen, Sofia E. Kjellman, Petra M. Langebroek, Florian Mekhaldi, Kevin S. Rozmiarek, Jonathan W. Rheinlænder, Margit Simon, Giulia Sinnl, Silje Smith-Johnsen, and James W. C. White

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Short summary
We use a series of spectral techniques to quantify the strength of high-frequency climate variability in Northeastern Greenland to 50,000 ka before present. Importantly, we find that variability consistently decreases hundreds of years prior to Dansgaard-Oeschger warming events. Model simulations suggest a change in North Atlantic sea ice behavior contributed to this pattern, thus providing new information on the conditions which proceeded abrupt climate change during the Last Glacial Period.