Search for: All records

Chemical anomalies in polar ice core records are frequently linked to volcanism; however, without the presence of (crypto)tephra particles, links to specific eruptions remain speculative. Correlating tephras yields estimates of eruption timing and potential source volcano, offers refinement of ice core chronologies, and provides insights into volcanic impacts. Here, we report on sparse rhyolitic glass shards detected in the Roosevelt Island Climate Evolution (RICE) ice core (West Antarctica), attributed to the 1.8 ka Taupō eruption (New Zealand)—one of the largest and most energetic Holocene eruptions globally. Six shards of a distinctive geochemical composition, identical within analytical uncertainties to proximal Taupō glass, are accompanied by a single shard indistinguishable from glass of the ~25.5 ka Ōruanui supereruption, also from Taupō volcano. This double fingerprint uniquely identifies the source volcano and helps link the shards to the climactic phase of the Taupō eruption. The englacial Taupō-derived glass shards coincide with a particle spike and conductivity anomaly at 278.84 m core depth, along with trachytic glass from a local Antarctic eruption of Mt. Melbourne. The assessed age of the sampled ice is 230 ± 19 CE (95% confidence), confirming that the published radiocarbon wiggle-match date of 232 ± 10 CE (2 SD) for the Taupō eruption is robust.

 

Abstract. In 2013 an ice core was recovered from Roosevelt Island, an ice dome between two submarine troughs carved by paleo-ice-streams in the Ross Sea, Antarctica. The ice core is part of the Roosevelt Island Climate Evolution (RICE) project and provides new information about the past configuration of the West Antarctic Ice Sheet (WAIS) and its retreat during the last deglaciation. In this work we present the RICE17 chronology, which establishes the depth–age relationship for the top 754 m of the 763 m core. RICE17 is a composite chronology combining annual layer interpretations for 0–343 m (Winstrup et al., 2019) with new estimates for gas and ice ages based on synchronization of CH4 and δ18Oatm records to corresponding records from the WAIS Divide ice core and by modeling of the gas age–ice age difference. Novel aspects of this work include the following: (1) an automated algorithm for multiproxy stratigraphic synchronization of high-resolution gas records; (2) synchronization using centennial-scale variations in methane for pre-anthropogenic time periods (60–720 m, 1971 CE to 30 ka), a strategy applicable for future ice cores; and (3) the observation of a continuous climate record back to ∼65 ka providing evidence that the Roosevelt Island Ice Dome was a constant feature throughout the last glacial period. 

Abstract. We present a 2700-year annually resolved chronology and snow accumulationhistory for the Roosevelt Island Climate Evolution (RICE) ice core, Ross IceShelf, West Antarctica. The core adds information on past accumulationchanges in an otherwise poorly constrained sector of Antarctica. The timescale was constructed by identifying annual cycles inhigh-resolution impurity records, and it constitutes the top part of theRoosevelt Island Ice Core Chronology 2017 (RICE17). Validation by volcanicand methane matching to the WD2014 chronology from the WAIS Divide ice coreshows that the two timescales are in excellent agreement. In a companionpaper, gas matching to WAIS Divide is used to extend the timescale for thedeeper part of the core in which annual layers cannot be identified. Based on the annually resolved timescale, we produced a record of past snowaccumulation at Roosevelt Island. The accumulation history shows thatRoosevelt Island experienced slightly increasing accumulation rates between700 BCE and 1300 CE, with an average accumulation of 0.25±0.02 mwater equivalent (w.e.) per year. Since 1300 CE, trends in the accumulationrate have been consistently negative, with an acceleration in the rate ofdecline after the mid-17th century. The current accumulation rate atRoosevelt Island is 0.210±0.002 m w.e. yr−1 (average since 1965 CE, ±2σ), and it is rapidly declining with a trend corresponding to0.8 mm yr−2. The decline observed since the mid-1960s is 8 times fasterthan the long-term decreasing trend taking place over the previouscenturies, with decadal mean accumulation rates consistently being belowaverage. Previous research has shown a strong link between Roosevelt Islandaccumulation rates and the location and intensity of the Amundsen Sea Low,which has a significant impact on regional sea-ice extent. The decrease inaccumulation rates at Roosevelt Island may therefore be explained in termsof a recent strengthening of the ASL and the expansion of sea ice in the easternRoss Sea. The start of the rapid decrease in RICE accumulation ratesobserved in 1965 CE may thus mark the onset of significant increases inregional sea-ice extent. 

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.