A 2700-year annual timescale and accumulation history for an ice core from Roosevelt Island, West Antarctica

Abstract

Abstract. We present a 2700-year annually resolved chronology and snow accumulation history for the Roosevelt Island Climate Evolution (RICE) ice core, Ross Ice Shelf, West Antarctica. The core adds information on past accumulation changes in an otherwise poorly constrained sector of Antarctica. The timescale was constructed by identifying annual cycles in high-resolution impurity records, and it constitutes the top part of the Roosevelt Island Ice Core Chronology 2017 (RICE17). Validation by volcanic and methane matching to the WD2014 chronology from the WAIS Divide ice core shows that the two timescales are in excellent agreement. In a companion paper, gas matching to WAIS Divide is used to extend the timescale for the deeper part of the core in which annual layers cannot be identified. Based on the annually resolved timescale, we produced a record of past snow accumulation at Roosevelt Island. The accumulation history shows that Roosevelt Island experienced slightly increasing accumulation rates between 700 BCE and 1300 CE, with an average accumulation of 0.25±0.02 m water equivalent (w.e.) per year. Since 1300 CE, trends in the accumulation rate have been consistently negative, with an acceleration in the rate of decline after the mid-17th century. The current accumulation rate at Roosevelt 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 to 0.8 mm yr−2. The decline observed since the mid-1960s is 8 times faster than the long-term decreasing trend taking place over the previous centuries, with decadal mean accumulation rates consistently being below average. Previous research has shown a strong link between Roosevelt Island accumulation rates and the location and intensity of the Amundsen Sea Low, which has a significant impact on regional sea-ice extent. The decrease in accumulation rates at Roosevelt Island may therefore be explained in terms of a recent strengthening of the ASL and the expansion of sea ice in the eastern Ross Sea. The start of the rapid decrease in RICE accumulation rates observed in 1965 CE may thus mark the onset of significant increases in regional sea-ice extent.

Refractory black carbon (rBC) variability in a 47-year West Antarctic snow and firn core

“…-Thompson et al (1999). f From Witherow and Lyons (2008). snow accumulation than the higher-altitude core (THW2010 -2020 m a.s.l.)…”

An 83 000-year-old ice core from Roosevelt Island, Ross Sea, Antarctica

“…Data from the RICE ice core plotted on the RICE17 agescale. (a) RICE methane and (c) δ 18 O atm records (gray) shown in comparison to target records from the WAIS Divide ice core on the WD2014 age-scale (Rhodes et al, 2015;Buizert et al, 2015b) (red) and NGRIP ice core (Baumgartner et al, 2014;Landais et al, 2007) on a modified GICC05modelext chronology (Wolff et al, 2010) (green). Solid triangles above panel (a) are gas age constraints from a Monte Carlo analysis; open diamonds are prior ACPs from visual matching (see text).…”

Constraining Geothermal Flux at Coastal Domes of the Ross Ice Sheet, Antarctica

“…We use a modern surface temperature of −24 °C, ice thickness of 765 m (Bertler et al, 2018), and accumulation rate of 0.22 m/a ice eq. ( Winstrup et al, 2019). The onset of divide flow occurs between 4 and 3 ka (Conwat et al, 1999;Martín et al, 2006;Winstrup et al, 2019).…”

“…( Winstrup et al, 2019). The onset of divide flow occurs between 4 and 3 ka (Conwat et al, 1999;Martín et al, 2006;Winstrup et al, 2019). The geothermal flux at Roosevelt Island is 84 ± 13 mW/m 2 using the basal temperature constraint of −4.3°C.…”