Ice drilling on Skytrain Ice Rise and Sherman Island, Antarctica

Abstract

To understand the long-term climate and glaciological evolution of the ice sheet in the region bordering the Weddell Sea, the British Antarctic Survey has undertaken a series of successful ice core projects drilling to bedrock on Berkner Island, James Ross Island and the Fletcher Promontory. A new project, WACSWAIN, seeks to increase this knowledge by further drilling to bedrock on two further ice rises in this region. In a single-season project, an ice core was recovered to bedrock at 651 m on Skytrain Ice Rise using an ice core drill in a fluid-filled borehole. In a second season, a rapid access drill was used to recover ice chips to 323 m on Sherman Island in a dry borehole, though failing to reach the bedrock which was at an estimated depth of 428 m.

Phase-sensitive radar as a tool for measuring firn compaction

“…a −1 , which exceeds the revised 0.30 m i.e. a −1 multi-centennial-averaged rate measured by Mulvaney and others (personal communication from R. Mulvaney, 2021). Both accumulation estimates are in agreement with accumulation rates from RACMO, 0.38 ± 0.08 m i.e.…”

“…In comparison, multi-centennial-averaged accumulation rates measured from the SIR ice core are 0.15 ± 0.02 m i.e. a −1 Elizabeth Case and Jonathan Kingslake (personal communication from R. Mulvaney, 2021). RACMO accumulation rates in the area are slightly higher, at 0.23 ± 0.05 m i.e.…”

“…pRES was deployed at 31 points on 7-11 December 2013 and 8-11 January 2015 along a 5.2 km transect perpendicular to and crossing the divide, centered on the location of a full-depth ice core (−79.741°, −78.545°; Fig. 1c; personal communication from R. Mulvaney, 2021).…”

“…where c is the speed of light in a vacuum (2.998 × 10 8 m s −1 ) and the refractive index, n, depends on density through Mulvaney and others (2014) and personal communication from R. Mulvaney (2021), where accumulation rates are recent, multi-centennial averages (∼1000 years). Ice densities were measured in the field during drilling of ice cores on FP (Mulvaney and others, 2014) and SIR (personal communication from R. Mulvaney, 2020).…”

“…To conserve mass globally and allow a steady state to be reached, we impose a lower boundary condition w(z t ) =ḃ, whereḃ is the ice-equivalent accumulation rate found in Section 2.4 at all locations except those nearest to the FP and ST ice cores, where icecore-measured rates are used instead (Table 1, personal communication from R. Mulvaney, 2021). For temperature boundary conditions (Eqn ( 18)) we used the mean annual surface temperatures listed in Table 1 at the model's upper boundary and at the model's lower boundary we used the temperature gradient measured at FP at the depth where ρ = 900 kg m −3 , ∂u/∂z = 0.0034 K m −1 .…”