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A large volcanic sulfate increase observed in ice core records around 1450 C.E. has been attributed in previous studies to a volcanic eruption from the submarine Kuwae caldera in Vanuatu. Both EPMA–WDS (electron microprobe analysis using a wavelength dispersive spectrometer) and SEM–EDS (scanning electron microscopy analysis using an energy dispersive spectrometer) analyses of five microscopic volcanic ash (cryptotephra) particles extracted from the ice interval associated with a rise in sulfate ca. 1458 C.E. in the South Pole ice core (SPICEcore) indicate that the tephra deposits are chemically distinct from those erupted from the Kuwae caldera. Recognizing that the sulfate peak is not associated with the Kuwae volcano, and likely not a large stratospheric tropical eruption, requires revision of the stratospheric sulfate injection mass that is used for parameterization of paleoclimate models. Future work is needed to confirm that a volcanic eruption from Mt. Reclus is one of the possible sources of the 1458 C.E. sulfate anomaly in Antarctic ice cores.

 

Abstract. The South Pole Ice Core (SPICEcore) was drilled in 2014–2016 to provide adetailed multi-proxy archive of paleoclimate conditions in East Antarcticaduring the Holocene and late Pleistocene. Interpretation of these recordsrequires an accurate depth–age relationship. Here, we present the SPICEcore (SP19) timescale for the age of the ice of SPICEcore. SP19 is synchronized to theWD2014 chronology from the West Antarctic Ice Sheet Divide (WAIS Divide) icecore using stratigraphic matching of 251 volcanic events. These eventsindicate an age of 54 302±519 BP (years before 1950) at thebottom of SPICEcore. Annual layers identified in sodium and magnesium ionsto 11 341 BP were used to interpolate between stratigraphic volcanic tiepoints, yielding an annually resolved chronology through the Holocene.Estimated timescale uncertainty during the Holocene is less than 18 yearsrelative to WD2014, with the exception of the interval between 1800 to 3100BP when uncertainty estimates reach ±25 years due to widely spacedvolcanic tie points. Prior to the Holocene, uncertainties remain within 124 years relative to WD2014. Results show an average Holocene accumulation rateof 7.4 cm yr−1 (water equivalent). The time variability of accumulation rateis consistent with expectations for steady-state ice flow through the modernspatial pattern of accumulation rate. Time variations in nitrateconcentration, nitrate seasonal amplitude and δ15N of N2 in turn are as expected for the accumulation rate variations. The highlyvariable yet well-constrained Holocene accumulation history at the site canhelp improve scientific understanding of deposition-sensitive climateproxies such as δ15N of N2 and photolyzed chemicalcompounds. 

A comprehensive record (WHV2020) of explosive volcanic eruptions in the last 11,000 years is reconstructed from the West Antarctica Ice Sheet Divide deep ice core (WDC). The chronological list of 426 large volcanic eruptions in the Southern Hemisphere and the low latitudes during the Holocene are of the highest quality of all volcanic records from ice cores, owing to the high‐resolution chemical measurement of the ice core and the exceptionally accurate WDC timescale. No apparent trend is found in the frequency (number of eruptions per millennium) of volcanic eruptions, and the number of eruptions in the most recent millennium (1,000–2,000 CE) is only slightly higher than the average in the last 11 millennia. The atmospheric aerosol mass loading of climate‐impacting sulfur, estimated from measured volcanic sulfate deposition, is dominated by explosive eruptions with extraordinarily high sulfur mass loading. Signals of three major volcanic eruptions are detected in the second half of the 17th century (1700–1600) BCE when the Thera volcano in the eastern Mediterranean was suspected to have erupted; the fact that these signals are synchronous with three volcanic eruptions detected in Greenland ice cores suggests that these are likely eruptions in the low latitudes and none should be attributed exclusively to Thera. A number of eruptions with very high sulfur mass loading took place shortly before and during an early Holocene climatic episode, the so‐called 8.2 ka event, and are speculated to have contributed to the initiation and magnitude of the cold event.

 

Variability in sea ice is a critical climate feedback, yet the seasonal behavior of Southern Hemisphere sea ice and climate across multiple timescales remains unclear. Here, we develop a seasonally resolved Holocene sea salt record using major ion measurements of the South Pole Ice Core (SPC14). We combine the SPC14 data with the GEOS‐Chem chemical transport model to demonstrate that the primary sea salt source switches seasonally from open water (summer) to sea ice (winter), with wintertime variations disproportionately responsible for the centennial to millennial scale structure in the record. We interpret increasing SPC14 and circum‐Antarctic Holocene sea salt concentrations, particularly between 8 and 10 ka, as reflecting a period of winter sea ice expansion. Between 5 and 6 ka, an anomalous drop in South Atlantic sector sea salt indicates a temporary sea ice reduction that may be coupled with Northern Hemisphere cooling and associated ocean circulation changes.