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Postglacial diatom-climate responses in a small lake in the Pacific Northwest of North America - Cores collected from Moss Lake, WA, USA have been analysed for diatoms and pollen as well as LOI and magnetic susceptibility, age/depth model output

posted on 2021-09-22, 12:29 authored by Joanne Egan, William J Fletcher, Timothy E. H. Allott
Data provided here includes a Holocene diatom and pollen record from Moss Lake, Washington, USA (N 47o 41' 35.7" W 121o 50' 48.6"). Cores from Moss Lake were collected in 2014 and contain tephra deposits from Mount Mazama and Glacier Peak. Investigations have been carried out on the impact of tephra deposition, but this publication analyses the whole Holocene record. Included in this data set are the raw diatom and pollen counts, sedimentary analyses including Loss on Ignition (raw and interpolated values) and magnetic susceptibility (using a loop scanner), and Radiocarbon dates including the output from an age/depth model created using OxCal. Abstract A diatom record spanning the last 14,500 cal yr BP from Moss Lake, Washington, USA is used to assess Holocene climate change in the Pacific Northwest including evidence for periodicities related to atmospheric-ocean interactions and/or variations in solar output and is directly compared to the pollen record from the same site. Three main climate phases were identified: (i) the Late Pleistocene (until 11,800 Cal yr BP, GI-1, GS-1), with a cold climate evidenced by the low abundance of diatoms; (ii) Greenlandian/early Northgrippian (11,800 - 7500 Cal yr BP), with a shift to a warmer climate,; and (iii) late Northgrippian and Meghalayan from 7500 Cal yr BP onwards, with a cooler and moist climate. These climate shifts are in good agreement with the pollen record of Moss Lake and other records from the region. Fluctuations in Discostella pseudostelligera and Aulacoseira taxa suggest climatic cycles of varying amplitude throughout the assemblage and are conceptually linked to ENSO/PDO like cycles. Spectral analyses revealed periodicities of approximately 2100 yrs, 1400 yrs, and 450 yrs. The ~2100 yr cycle is attributed to solar variation, particularly the Hallstatt Oscillation. Both the ~1400 yr and ~450 yr cycles are attributed to ENSO and PDO like cycles. The ~1400 periodicity is evident throughout the Late Pleistocene and late Northgrippian/Meghalayan reflecting high amplitude shifts from El Niño/positive PDO (weak wind intensity) to La Niña/Negative PDO (high wind intensity). The cycle amplitudes are reduced during the Greenlandian and occur on a 450-year cycle. ENSO suppression is recorded throughout the Pacific Northwest, but most state it occurred during the Northgrippian, suggesting the diatom record from Moss Lake is modulated by endogenic processes during this time. Diatom data from Moss Lake has helped to refine our understanding of Holocene climate change and ENSP/PDO in the Pacific Northwest.


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