the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Early Holocene ice on the Begguya plateau (Mt. Hunter, Alaska) revealed by ice core 14C age constraints
Ling Fang
Dominic Winski
Karl Kreutz
Hanna L. Brooks
Emma Erwin
Erich Osterberg
Seth Campbell
Cameron Wake
Margit Schwikowski
Abstract. Investigating North Pacific climate variability during warm intervals prior to the Common Era can improve our understanding of the behavior of ocean-atmosphere teleconnections between low latitudes and the Arctic under future warming scenarios. However, most of the existing ice core records from the Alaska/Yukon region only allow access to climate information covering the last few centuries. Here we present a surface-to-bedrock age scale for a 210-meter long ice core recovered in 2013 from the summit plateau of Begguya (Mt. Hunter; Denali National Park, Central Alaska). Combining dating by annual layer counting with absolute dates from micro-radiocarbon dating, a continuous chronology for the entire ice core archive was established using an ice flow model. Calibrated 14C ages from the deepest section (209.1 m, 7.7 to 9.0 ka cal BP) indicate that basal ice on Begguya is at least of early Holocene origin. A series of samples from a shallower depth interval (199.8 to 206.6 m) were dated with near uniform 14C ages (3 to 5 ka cal BP). Our results suggest this may be related to an increase in annual net snow accumulation rates over this period following the Northern Hemisphere Holocene Climate Optimum (around 8 to 5 ka BP). With absolute dates constraining the timescale for the last > 8 ka, this paleo archive will allow future investigations of Holocene climate and the regional evolution of spatial and temporal changes in atmospheric circulation and hydroclimate in the North Pacific.
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Ling Fang et al.
Status: open (until 03 Jul 2023)
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RC1: 'Comment on tc-2023-54', Anonymous Referee #1, 02 Jun 2023
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This paper presents the first reliable record of early Holocene ice in the Alaskan high mountains, where many scientists have attempted to locate it for many years. The finding of this study have the potential to inspire further exploration of Alaskan glaciers as a valuable paleoclimate proxy. Therefore, I strongly recommend the editor to accept this manuscript for publication in The Cryosphere. The manuscript is well-written, and the figures and tables are presented accurately. However, I would like to suggest the inclusion of several additional references that the authors may have overlooked.
Sasaki, H., Matoba, S., Shiraiwa, T. and Benson, C.S., Temporal variation in iron flux deposition onto the Northern North Pacific reconstructed from an ice core drilled at Mount Wrangell, Alaska, SOLA, 2016, 12, 287-290. DOI:10.2151/sola.2016-056.
https://www.jstage.jst.go.jp/article/sola/12/0/12_2016-056/_pdf/-char/ja
Shiraiwa, T., Goto-Azuma, K., Matoba, S., Yamasaki, T., Segawa, T., Kanamori, S., Matsuoka, K. and Fujii, Y., Ice core drilling at King Col, Mount Logan 2002, Bulletin of Glaciological Research, 2003, 20, 57-63.
https://web.seppyo.org/bgr/pdf/20/BGR20P57.pdf
Citation: https://doi.org/10.5194/tc-2023-54-RC1 -
RC2: 'Comment on tc-2023-54', Anonymous Referee #2, 03 Jun 2023
reply
This manuscript presents the 14C ages of the a 210-meter long ice core drilled to the bottom from the summit plateau of Begguya (Mt. Hunter; Denali National Park, Central Alaska). The authors conclued that the basal ice on Begguya is at least of early Holocene origin, thus providing a potential paleo archive of Holocene climate in the North Pacific region. The results are reliable and the manuscript is well written.
There are a few concerns that the authors may need to consider when revising the manuscript.
(1) In Figure 1, some of the ages below the ice core drilling sites may be misleading. For instance, the Aurora Peak ice core is with a length of 180.17m, while the age of 1734 CE corresponds to the depth of 149.68m w.eq. The authors need to verify if this age of 1734 CE refers to the basal ice? if not, how far the ice corresponding to 1734 CE is above the bottom? The same kind of verification is necessary for all the other ice cores shown in Figure 1.
(2) Lines 116-117. Please confirm if or not this work provides the first radiometrically dated high latitude Northern Hemisphere ice core chronology?
(3) sections 2.1 and 3.2. Parts of the contents in these two sections duplicate.
(4) The author may want to consider moving section 3.1 into section 2.
(5) Lines 252-254. Slightly?
Citation: https://doi.org/10.5194/tc-2023-54-RC2
Ling Fang et al.
Ling Fang et al.
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