Holocene climate changes in eastern Beringia (NW North America) - A systematic review of multi-proxy evidence

QUATERNARY SCIENCE REVIEWS

卷:147

Article; Proceedings Paper

Kaufman, Darrell S.¹  Axford, Yarrow L.²  Henderson, Andrew C. G.³  McKay, Nicholas P.¹  Oswald, W. Wyatt⁴  Saenger, Casey⁵  Anderson, R. Scott¹  Bailey, Hannah L.³  Clegg, Benjamin⁶  Gajewski, Konrad⁷  Hu, Feng Sheng^8,9  Jones, Miriam C.¹⁰  Massa, Charly¹¹  Routson, Cody C.¹  Werner, Al¹²  Wooller, Matthew J.¹³  Yu, Zicheng¹¹ 

[1] No Arizona Univ, Sch Earth Sci & Environm Sustainabil, Flagstaff, AZ 86011 USA

[2] Northwestern Univ, Dept Earth & Planetary Sci, Evanston, IL 60208 USA

[3] Newcastle Univ, Sch Geog Polit & Sociol, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England

[4] Emerson Coll, Inst Liberal Arts & Interdisciplinary Studies, Boston, MA 02116 USA

[5] Univ Washington, Joint Inst Study Atmosphere & Ocean, Seattle, WA 98105 USA

[6] Univ Illinois, Sch Integrat Biol, Urbana, IL 61801 USA

[7] Univ Ottawa, Dept Geog, Ottawa, ON K1N 6N5, Canada

[8] Univ Illinois, Dept Plant Biol, Urbana, IL 61801 USA

[9] Univ Illinois, Dept Geol, Urbana, IL 61801 USA

[10] US Geol Survey, Eastern Geol & Paleoclimate Sci Ctr, Reston, VA 20192 USA

[11] Lehigh Univ, Dept Earth & Environm Sci, Bethlehem, PA 18015 USA

[12] Mt Holyoke Coll, Dept Geol, S Hadley, MA 01075 USA

[13] Univ Alaska Fairbanks, Sch Fisheries & Ocean Sci, Water & Environm Res Ctr, Fairbanks, AK 99775 USA

关键词: Holocene;    Paleoclimate;    Beringia;    Alaska;    Yukon;    Synthesis;    Multi-proxy;    Climate change;   

DOI  :  10.1016/j.quascirev.2015.10.021

来源: Elsevier

【 摘 要 】

Reconstructing climates of the past relies on a variety of evidence from a large number of sites to capture the varied features of climate and the spatial heterogeneity of climate change. This review summarizes available information from diverse Holocene paleoenvironmental records across eastern Beringia (Alaska, westernmost Canada and adjacent seas), and it quantifies the primary trends of temperature- and moisture-sensitive records based in part on midges, pollen, and biogeochemical indicators (compiled in the recently published Arctic Holocene database, and updated here to v2.1). The composite time series from these proxy records are compared with new summaries of mountain-glacier and lake-level fluctuations, terrestrial water-isotope records, sea-ice and sea-surface-temperature analyses, and peatland and thaw-lake initiation frequencies to clarify multi-centennial- to millennial-scale trends in Holocene climate change. To focus the synthesis, the paleo data are used to frame specific questions that can be addressed with simulations by Earth system models to investigate the causes and dynamics of past and future climate change. This systematic review shows that, during the early Holocene (11.7-8.2 ka; 1 ka = 1000 cal yr BP), rather than a prominent thermal maximum as suggested previously, temperatures were highly variable, at times both higher and lower than present (approximate mid-20th-century average), with no clear spatial pattern. Composited pollen, midge and other proxy records average out the variability and show the overall lowest summer and mean-annual temperatures across the study region during the earliest Holocene, followed by warming over the early Holocene. The sparse data available on early Holocene glaciation show that glaciers in southern Alaska were as extensive then as they were during the late Holocene. Early Holocene lake levels were low in interior Alaska, but moisture indicators show pronounced differences across the region. The highest frequency of both peatland and thaw-lake initiation ages also occurred during the early Holocene. During the middle Holocene (8.2-4.2 ka), glaciers retreated as the regional average temperature increased to a maximum between 7 and 5 ka, as reflected in most proxy types. Following the middle Holocene thermal maximum, temperatures decreased starting between 4 and 3 ka, signaling the onset of Neoglacial cooling. Glaciers in the Brooks and Alaska Ranges advanced to their maximum Holocene extent as lakes generally rose to modern levels. Temperature differences for averaged 500-year time steps typically ranged by 1-2 degrees C for individual records in the Arctic Holocene database, with a transition to a cooler late Holocene that was neither abrupt nor spatially coherent. The longest and highest-resolution terrestrial water isotope records previously interpreted to represent changes in the Aleutian low-pressure system around this time are here shown to be largely contradictory. Furthermore, there are too few records with sufficient resolution to identify sub-centennial-scale climate anomalies, such as the 8.2 ka event. The review concludes by suggesting some priorities for future paleoclimate research in the region. (C) 2015 Elsevier Ltd. All rights reserved.

【 授权许可】

Free