Modelling perennial firn aquifers in the Antarctic Peninsula (1979–2016)

Abstract

Abstract. We use two snow models, the IMAU Firn Densification Model (IMAU-FDM) and SNOWPACK, to model firn characteristics in the Antarctic Peninsula (AP). We force these models with mass and energy fluxes from the Regional Atmospheric Climate MOdel (RACMO2.3p2) to construct a 1979–2016 climatology of AP firn density, temperature and liquid water content. A comparison with 75 snow temperature observations at 10 m depth and with density from 11 firn cores, suggests that both snow models perform adequately. In this study, we focus on the detection of so-called perennial firn aquifers (PFAs), that are formed when surface meltwater percolates into the firnpack in summer, is then buried by snowfall, and does not refreeze during the following winter. In 941 model grid points, covering ~ 28,000 km2, PFAs existed for at least one year in the simulated period, most notably in the western AP. At these locations, surface meltwater production exceeds 150 to 300 mm w.e. yr−1, with accumulation at least an order of magnitude larger. Most pronounced and widespread are PFAs modelled on and around Wilkins ice shelf. Here, both meltwater production and accumulation rates are sufficiently high to cause PFA formation in most years in the 1979–2016 period, covering a large part of the ice shelf. Other notable PFA locations are Wordie ice shelf, an ice shelf that has almost completely disappeared in recent decades, and the relatively warm northwestern mountain ranges of Palmer Land, where accumulations rates can be extremely large and PFAs are formed frequently. We find that not only the magnitude of melt and accumulation is important, but also the timing. If large accumulation events occur in the months following an above average summer melt event, this favours PFA formation in that year. Finally, we find that most PFAs are predicted near the grounding lines of the (former) Prince Gustav, Wilkins and Wordie ice shelves. This highlights the need to further investigate how PFAs may impact ice shelf disintegration events, in a similar way as supraglacial lakes do.

Hydrologic Properties of a Highly Permeable Firn Aquifer in the Wilkins Ice Shelf, Antarctica

“…per year and melt rates are >650 mm WEyr −1 (Bell et al, 2018;Montgomery et al, 2020;Noël et al, 2018). For the AIS, areas with similar surface melt and snow accumulation signatures are rare, though recent modeling studies show widespread perennial firn aquifers on the Wilkins Ice Shelf (WIS) and elsewhere on the Antarctic Peninsula (van Wessem et al, 2016(van Wessem et al, , 2020. These aquifers can contribute to sea-level rise if connected to the ocean by slowly draining into crevasses (Koenig et al, 2014) and are especially important to understand on ice shelves where meltwater storage is likely a precursor to hydrofracture and ice shelf break-ups (Bell et al, 2018;Scambos et al, 2000).…”

Antarctic Atmospheric River Climatology and Impacts

“…The prevalence of perennial rn aquifers on the Wilkins ice shelf may explain the disparity between AR occurrences and calving/collapse events (van et al [2020]). These features where meltwater percolates in the snowpack and then remains buried under snow as a liquid before eventually draining into crevasses (Alley et al [2018]), occur in areas with high snowfall accumulation like the Wilkins and can delay or reduce runo (van Wessem et al [2020]; Munneke et al [2014]). Still more research is needed to properly understand their impact on Antarctic ice-shelf stability.…”

Spectral snow albedo in a regional climate model: application to the Greenland and Antarctic ice sheets

“…It has been used to model the climate of the GrIS (Noël et al, 2018b;Noël et al, 2019) and AIS (Van Wessem et al, 2018), and smaller regions like the AP (Van Wessem et al, 2016) and the Canadian Arctic (Noël et al, 2018a). Furthermore, RACMO2 has been used to investigate physical processes like the snowmelt-albedo feedback (Jakobs et al, 2019), firn aquifers (Van Wessem et al, 2020) and föhn winds in the AP (Wiesenekker et al, 2018). Some processes, however, were not included up to recently, like subsurface heating by radiation penetration, or with a limited parameterization, like snow albedo.…”