Chronology and sedimentology of a new 2.9 ka annually laminated record from South Sawtooth Lake, Ellesmere Island in this NOAA depository: https://www.ncdc.noaa.gov/paleo/study/33214

Abstract

Few annually laminated (varved) lacustrine records exist in the Arctic, but these highresolution climate archives are needed to better understand abrupt climate change and the natural mode of climate variability of this sensitive region. This paper presents a new highresolution 2900-year long varved lake sediment record from the Fosheim Peninsula, Ellesmere Island. The varve chronology is based on multiple varve counts made on highresolution scanning electron microscope images of overlapping sediment thin sections, and is supported by several independent dating techniques, including 137 Cs and 210 Pb analysis, one optically stimulated luminescence age located close to the bottom of the composite sequence, and comparision between paleomagnetic variations of this record and the longest High-Arctic varve record, Lower Murray Lake, which confirms the reliability of the Sawtooth chronology. High resolution backscattered images examined under a scanning electron microscope (SEM) were crucial to giving a more detailed view of sedimentation processes in the lake and thus help to delineate varves more precisely than in conventional image analysis. Fine-scale geochemical analysis reveals that lake sedimentation is mainly clastic and that elemental geochemistry is influenced by grain-size. Principal component analysis of multiple proxies and the coarse grain-size fraction of South Sawtooth Lake display similar fluctuations to the nearby Agassiz Ice Cap ¶ 18 O record, including lower values during the Little Ice Age cold period. These results show this new high-resolution and continuous record has a reliable varve chronology and is sensitive to temperature variability. South Sawtooth Lake's mean sedimentation rate of 1.67 mm a -1 is higher than any other sedimentary sequence in the High Arctic providing a unique opportunity for extracting new, high-resolution paleoclimatological and paleoenvironmental record.

Annually resolved Atlantic sea surface temperature variability over the past 2,900 y

“…South Sawtooth Lake (hereafter SSL; Fig. 1 A ), located on the Fosheim Peninsula, Ellesmere Island, is an 80-m-deep lake ( 16 , 18 ) which became ice-free between 8,000 and 6,000 y cal B.P. ( 19 ).…”

“…( 19 ). Previous studies have shown that the sedimentary record contains clastic varves (annual laminations) and that the main sediment fluxes to the lake are primarily driven by snowmelt and occasional summer rainfall events ( 16 , 20 ). The presence of several river channels that converge into one main inlet on the east side of the catchment makes it an ideal lake to study the hydroclimate of this region ( SI Appendix , Fig.…”

“…Furthermore, the lake’s bathymetry is characterized by a sill between the two basins preventing coarse-grained sediments to reach the coring site ( 20 ). Computerized tomography scans (which provide three-dimensional density data) and sediment accumulation rates indicate that the input of clastic sediment was very constant and uniform throughout the past 2,900 y ( 16 ). The varve chronology is based on multiple varve counts made on scanning electron microscope (SEM) images of 100 overlapping thin sections and is confirmed by several independent dating techniques ( 16 ).…”

“…Map created using University of Maine Climate Reanalyzer, https://climatereanalyzer.org/ . ( B ) Annually fine grain size (% <16 µm) ( 16 ) compared to Ti at SSL (cps: counts per second) over the past 2,900 y. Data are filtered by an 11-y Gaussian filter.…”

“…( C , Lower ) Same as Upper , but using the unsmoothed (and unaltered) instrumental AMV from Kaplan SST ( 17 ). Note that a turbidite dated to 1990 eroded 9 varves ( 16 ).…”