Net accumulation rates derived from ice core stable isotope records of Pío XI glacier, Southern Patagonia Icefield

Abstract

Abstract. Pío XI, the largest glacier of the Southern Patagonia Icefield, reached its neoglacial maximum extent in 1994 and is one of the few glaciers in that area which is not retreating. In view of the recent warming it is important to understand glacier responses to climate changes. Due to its remoteness and the harsh conditions in Patagonia, no systematic mass balance studies have been performed. In this study we derived net accumulation rates for the period 2000-2006 from a 50 m (33.2 4 m weq) ice core collected in the accumulation area of Pío XI (2600 m a.s.l., 49 • 16 40 S, 73 • 21 14 W). Borehole temperatures indicate near temperate ice, but the average melt percent is only 16 ± 14%. Records of stable isotopes are well preserved and were used for identification of annual layers. Net accumulation rates range from 3.4-7.1 water equivalent (m weq) with an average of 5.8 m weq, comparable to precipitation amounts at the Chilean coast, but not as high as expected for the Icefield. Ice core stable isotope data correlate well with upper air temperatures and may be used as temperature proxy.

Quantifying mass balance processes on the Southern Patagonia Icefield

“…and on the outlet glacier tongues it reaches down to −15 m w.e. The direct (point) observations of the surface mass balance on the SPI are restricted to a network of ablation stakes with changing configuration on the Perito Moreno glacier during 1995(Stuefer et al, 2007, a tower installed near the equilibrium line of the Chico glacier where yearly surface mass balance values at one point were obtained from 1994 to 2002 (Rivera, 2004) and four firn cores in the accumulation areas of the Moreno (Aristarain and Delmas, 1993), Tyndall (Shiraiwa et al, 2002), Chico (Schwikowski et al, 2006) and PioXI glaciers (Schwikowski et al, 2013). In Fig.…”

“…These two points correspond to firn cores taken on high peaks in the accumulation areas of the Perito Moreno and PioXI glaciers. The probably large amounts of snow falling at this locations do not persist on the windexposed peaks (Schwikowski et al, 2013). Indeed, some ice core drilling sites were specifically chosen to minimize accumulation compared to the surroundings, to obtain longer time series in the shallow ice cores (Schwikowski et al, 2006).…”

Extreme Precipitation and Climate Gradients in Patagonia Revealed by High-Resolution Regional Atmospheric Climate Modeling

“…Therefore, the local firn acts as a robust ''archiver'' of past accumulation, particularly because annual layers can be easily detected given that the seasonal variability of temperature, and hence oxygen isotope ratio, is large (Schwikowski et al 2013). Figure 8c displays the annual mean simulated SMB on the NPI and SPI, along with available SMB observations from firn cores ( Table 2).…”

“…Because of their remoteness and harsh climate, observations of SMB on the ice fields are scarce and sometimes difficult to interpret; the few measurements indicate locally extremely high annual SMB of .5 to 15 m w.e. (Matsuoka and Naruse 1999;Schwikowski et al 2013), significantly more than most other glaciated regions on earth.…”

“…Precipitation on the upper ice fields generally falls as snow, and at this elevation meltwater generally refreezes in the snowpack (Schwikowski et al 2013). Therefore, the local firn acts as a robust ''archiver'' of past accumulation, particularly because annual layers can be easily detected given that the seasonal variability of temperature, and hence oxygen isotope ratio, is large (Schwikowski et al 2013).…”