A 2000-year annual record of snow accumulation rates for Law Dome, East Antarctica

Abstract

Abstract. Accurate high-resolution records of snow accumulation rates in Antarctica are crucial for estimating ice sheet mass balance and subsequent sea level change. Snowfall rates at Law Dome, East Antarctica, have been linked with regional atmospheric circulation to the mid-latitudes as well as regional Antarctic snowfall. Here, we extend the length of the Law Dome accumulation record from 750 years to 2035 years, using recent annual layer dating that extends to 22 BCE. Accumulation rates were calculated as the ratio of measured to modelled layer thicknesses, multiplied by the long-term mean accumulation rate. The modelled layer thicknesses were based on a power-law vertical strain rate profile fitted to observed annual layer thickness. The periods 380–442, 727–783 and 1970–2009 CE have above-average snow accumulation rates, while 663–704, 933–975 and 1429–1468 CE were below average, and decadal-scale snow accumulation anomalies were found to be relatively common (74 events in the 2035-year record). The calculated snow accumulation rates show good correlation with atmospheric reanalysis estimates, and significant spatial correlation over a wide expanse of East Antarctica, demonstrating that the Law Dome record captures larger-scale variability across a large region of East Antarctica well beyond the immediate vicinity of the Law Dome summit. Spectral analysis reveals periodicities in the snow accumulation record which may be related to El Niño–Southern Oscillation (ENSO) and Interdecadal Pacific Oscillation (IPO) frequencies.

Regional Antarctic snow accumulation over the past 1000 years

“…Further refinement to this approximation was suggested by Dansgaard and Johnsen (1969) who proposed a piecewise linear vertical strain rate profile, constant in the upper portion of the ice sheet and below that decreasing linearly to zero at the base of the ice sheet, or a non-zero value in the presence of basal melt. Roberts et al (2015) show that a more realistic vertical strain rate profile, based on the power-law distribution of horizontal velocity of Lliboutry (1979), may provide a better estimate of strain rate even in the upper portion of the ice sheet. Additionally, recently deployed ground-based phasesensitive ice-penetrating radar systems have demonstrated the ability to measure the vertical strain rate profile (Nicholls et al, 2015).…”

“…While the magnitude of snow accumulation varies along the Wilkes Land coast, the accumulation is temporally coherent at least as far away as the Shackleton Ice Shelf . In general, this region shows accumulation variability associated with both ENSO and IPO Vance et al, 2015), which influence the meridional component of the large-scale circulation (van Ommen and Morgan, 2010; Roberts et al, 2015;Vance et al, 2015).…”

Optimal site selection for a high-resolution ice core record in East Antarctica

“…Three sites that do largely meet these criteria are the recently obtained West Antarctic Ice Sheet (WAIS) Divide core in West Antarctica (79.767 • S, 112.133 • W; 1766 m elevation) (Bisiaux et al, 2012), the James Ross Island core in the northern Antarctic Peninsula region (57.685 • W, 64.2017 • S; 1252 m elevation) (Abram et al, 2011;Mulvaney et al, 2012) and the Law Dome core (112.8069 • W, 66.7697 • S; 1370 m elevation) (Morgan et al, 1997;Roberts et al, 2015) in coastal East Antarctica. Airborne surveys across large swathes of East Antarctica (e.g.…”

Reply to comment by E. W. Wolff et al. on “Low time resolution analysis of polar ice cores cannot detect impulsive nitrate events”

“…The Law Dome ice core [ Palmer et al , ] cited by Wolff et al [] as a discretely sampled, very fine resolution core to dispute identification of nitrate spikes from SPEs is a poor example because this core (with at best 2 month resolution for 1840–1880) (like Halley) was drilled at a coastal site and reflects primarily a maritime climate. Palmer et al [] and Roberts et al [] both stated this caveat clearly in their papers. The fact that statistical evidence for SPEs was found in this core with these resolution and location limitations is remarkable.…”