noaa-lake-6197 Iceberg Lake, Alaska 1,500 Year Varve Thickness and Temperature Reconstruction Loso, M.G. Iceberg Lake, Alaska 1,500 Year Varve Thickness and Temperature Reconstruction 2008-11-01 NCDC-Paleoclimatology ONLINE Files Pending https://www.ncdc.noaa.gov/paleo/study/6197 Investigator M.G. Loso earth science paleoclimate climate reconstructions|paleolimnology temperature,varve thickness,95% confidence interval upper bound,degree Celsius,May-Jun,climate reconstructions|paleolimnology,anomalized|smoothed,null,N,anomalies from reconstructed mean temperatures of the last millennium; smoothed with a 24-year low-pass filter; based on varve thickness earth science paleoclimate paleolimnology varve thickness,null,null,millimeter,null,paleolimnology,null,null,N,section A earth science paleoclimate climate reconstructions|paleolimnology temperature,varve thickness,null,degree Celsius,May-Jun,climate reconstructions|paleolimnology,anomalized|smoothed,null,N,anomalies from reconstructed mean temperatures of the last millennium; smoothed with a 24-year low-pass filter; based on varve thickness earth science paleoclimate paleolimnology varve thickness,null,null,millimeter,null,paleolimnology,null,null,N,section B earth science paleoclimate paleolimnology varve thickness,null,null,millimeter,null,paleolimnology,null,null,N,section J earth science paleoclimate paleolimnology varve thickness,null,null,millimeter,null,paleolimnology,null,null,N,section K earth science paleoclimate paleolimnology varve thickness,null,null,millimeter,null,paleolimnology,composited,null,N,simple averages of data from individual sections earth science paleoclimate climate reconstructions|paleolimnology age,null,null,year Common Era,null,climate reconstructions|paleolimnology,null,null,N,null earth science paleoclimate paleolimnology varve thickness,null,null,millimeter,null,paleolimnology,null,null,N,section N earth science paleoclimate climate reconstructions|paleolimnology temperature,varve thickness,95% confidence interval lower bound,degree Celsius,May-Jun,climate reconstructions|paleolimnology,anomalized|smoothed,null,N,anomalies from reconstructed mean temperatures of the last millennium; smoothed with a 24-year low-pass filter; based on varve thickness earth science paleoclimate paleolimnology varve thickness,null,null,millimeter,null,paleolimnology,null,null,N,section M earth science paleoclimate paleolimnology varve thickness,null,null,millimeter,null,paleolimnology,null,null,N,section I earth science paleoclimate climate reconstructions|paleolimnology temperature,varve thickness,null,degree Celsius,May-Jun,climate reconstructions|paleolimnology,anomalized,null,N,anomalies from reconstructed mean temperatures of the last millennium; based on varve thickness earth science paleoclimate paleolimnology varve thickness,null,null,millimeter,null,paleolimnology,smoothed,null,N,40-year lowpass filter earth science paleoclimate paleolimnology physical properties geoscientificInformation Air Temperature Reconstruction PAGES 2k Network PAGES Arctic 2k 1508 cal yr BP -48 cal yr BP Complete 60.783 60.783 -142.95 -142.95 933 933 Continent North America United States Of America Alaska Iceberg Lake>LATITUDE 60.783>LONGITUDE -142.95 None Please cite original publication, online resource, dataset and publication DOIs (where available), and date accessed when using downloaded data. If there is no publication information, please cite investigator, title, online resource, and date accessed. The appearance of external links associated with a dataset does not constitute endorsement by the Department of Commerce/National Oceanic and Atmospheric Administration of external Web sites or the information, products or services contained therein. For other than authorized activities, the Department of Commerce/NOAA does not exercise any editorial control over the information you may find at these locations. These links are provided consistent with the stated purpose of this Department of Commerce/NOAA Web site. English DOC/NOAA/NESDIS/NCEI National Centers for Environmental Information, NESDIS, NOAA, U.S. Department of Commerce https://www.ncdc.noaa.gov/data-access/paleoclimatology-data DATA Center Contact Bruce Bauer bruce.a.bauer@noaa.gov paleo@noaa.gov 303-497-6280 303-497-6513

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Boulder CO 80305-3328 USA online ASCII Loso, M.G. 2009 Journal of Paleolimnology 41 1 117-128 10.1007/s10933-008-9264-9

For the heavily glaciated mountains of southern Alaska, few high-resolution, millennial-scale proxy temperature reconstructions are available for comparison with modern temperatures or with the history of glacier fluctuations. Recent catastrophic drainage of glacier-dammed Iceberg Lake, on the northern margin of the Bagley Icefield, exposed subaerial outcrops of varved lacustrine sediments that span the period 442-1998 AD. Here, an updated chronology of varve thickness measurements is used to quantitatively reconstruct melt-season temperature anomalies. From 1958 to 1998, varve thickness has a positive and marginally significant correlation with May-June temperatures at the nearest coastal measurement stations. Varve sensitivity to temperature has changed over time, however, in response to lake level changes in 1957 and earlier. I compensate for this by log-transforming the varve thickness chronology, and also by using a 400-year-long tree-ring-based temperature proxy to reconstruct melt-season temperatures at Iceberg Lake. Regression against this longer proxy record is statistically weak, but spans the full range of occupied lake levels and varve sensitivities. Reconstructed temperature anomalies have broad confidence intervals, but nominally span 1.1C over the last 1500+ years. Maximum temperatures occurred in the late twentieth century, with a minimum in the late sixth century. The Little Ice Age is present as three cool periods between 1350 and 1850 AD with maximum cooling around 1650 AD. A Medieval Warm Period is evident from 1000 to 1100 AD, but the temperature reconstruction suggests it was less warm than recent decades - an observation supported by independent geological evidence of recent glacier retreat that is unprecedented over the period of record. STUDY NOTES: Varve thickness measurements and temperature reconstruction from Iceberg Lake, Alaska

GET DATA https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/northamerica/usa/alaska/iceberg2008.txt GET DATA https://www1.ncdc.noaa.gov/pub/data/paleo/paleolimnology/northamerica/usa/alaska/iceberg2008.xls USA/NOAA DIF Version 9.8.4 2018-12-11 2018-12-11