Abstract
Abstract. A new ice core drilled at the South Pole provides a 54 000-year paleoenvironmental record including the composition of the past atmosphere. This paper describes the SP19 chronology for the South Pole atmospheric gas record and complements a previous paper (Winski et al., 2019) describing the SP19 ice chronology. The gas chronology is based on a discrete methane (CH4) record with 20- to 190-year resolution. To construct the gas timescale, abrupt changes in atmospheric CH4 during the glacial period and centennial CH4 variability during the Holocene were used to synchronize the South Pole gas record with analogous data from the West Antarctic Ice Sheet Divide ice core. Stratigraphic matching based on visual optimization was verified using an automated matching algorithm. The South Pole ice core recovers all expected changes in CH4 based on previous records. Gas transport in the firn results in smoothing of the atmospheric gas record with a smoothing function spectral width that ranges from 30 to 78 years, equal to 3 % of the gas-age–ice-age difference, or Δage. The new gas chronology, in combination with the existing ice age scale from Winski et al. (2019), allows a model-independent reconstruction of the gas-age–ice-age difference through the whole record, which will be useful for testing firn densification models.
Highlights
Ice core records provide detailed reconstructions of past climate in the polar regions and unique global records of the past atmosphere
To create a gas chronology for SPC14, CH4 variations were visually matched at equivalent rapid CH4 variations in the WD ice core; subsequently the match was optimized using an automated algorithm
The SPC14 CH4 record resolves the abrupt CH4 features associated with Heinrich events, as described by Rhodes et al (2015), and further resolves centennial-scale variations in CH4 previously described in the WD (Mitchell et al, 2013) and Roosevelt Island (RICE) ice cores (Lee et al, 2020a) and in several records by Rhodes et al (2017)
Summary
Ice core records provide detailed reconstructions of past climate in the polar regions and unique global records of the past atmosphere. These records are of high resolution and are well-dated, allowing comparisons to events in other ice cores and paleo-archives (Buizert et al, 2015; Elderfield et al, 2012; Hodell et al, 2017; Marcott et al, 2013). The recently collected South Pole ice core (SPC14) expands a spatial array of ice cores drilled across Antarctica that extend into the last glacial period.
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