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
dataset
posted on 2021-09-22, 12:29authored byJoanne Egan, William J Fletcher, Timothy E. H. Allott
Abstract
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.