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Ice cores contain stratigraphic records of microbial cells, buried through thousands of years of snow accumulation and spanning significant climatic periods. It is well established that microorganisms are transported to and preserved within the West Antarctic Ice Sheet. From the total assemblage of microorganisms that land on the ice sheet, we do not know how or if microorganisms survive burial and persist long-term in glacial ice equally. We cannot accurately interpret microbial cell stratigraphic records or utilize these cellular records as proxies until we understand post-depositional processes and the genomic adaptations of microbial cells in glacial ice. Here, we quantify cell concentrations in meltwater from four flow paths of a continuous flow analysis melter system in order to evaluate the efficacy of these flow paths for the successful collection of intact cells archived in ice cores. Using this information, we melted eight sections from the WAIS Divide ice core and quantified the cell concentrations, assayed the viability of the microbial cells, and sorted individual cells for genome sequencing. We will present preliminary data from the flow path cell recovery experiment, and genomic and viability results from the WAIS Divide ice core, with the hope to stimulate further discussion around single cell genomes and how they can be leveraged to complement paleoclimate information from ice cores. 

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. 

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.

 

High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually dated ice core record from the eastern Ross Sea, named the Roosevelt Island Climate Evolution (RICE) ice core. Comparison of this record with climate reanalysis data for the 1979–2012 interval shows that RICE reliably captures temperature and snow precipitation variability in the region. Trends over the past 2700 years in RICE are shown to be distinct from those in West Antarctica and the western Ross Sea captured by other ice cores. For most of this interval, the eastern Ross Sea was warming (or showing isotopic enrichment for other reasons), with increased snow accumulation and perhaps decreased sea ice concentration. However, West Antarctica cooled and the western Ross Sea showed no significant isotope temperature trend. This pattern here is referred to as the Ross Sea Dipole. Notably, during the Little Ice Age, West Antarctica and the western Ross Sea experienced colder than average temperatures, while the eastern Ross Sea underwent a period of warming or increased isotopic enrichment. From the 17th century onwards, this dipole relationship changed. All three regions show current warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea but increasing in the western Ross Sea. We interpret this pattern as reflecting an increase in sea ice in the eastern Ross Sea with perhaps the establishment of a modern Roosevelt Island polynya as a local moisture source for RICE.