An exploratory modelling study of perennial firn aquifers in the Antarctic Peninsula for the period 1979–2016

Abstract

Abstract. In this study, we focus on the model detection in the Antarctic Peninsula (AP) of so-called perennial firn aquifers (PFAs) that are widespread in Greenland and Svalbard and are formed when surface meltwater percolates into the firn pack in summer, which is then buried by snowfall and does not refreeze during the following winter. We use two snow models, the Institute for Marine and Atmospheric Research Utrecht Firn Densification Model (IMAU-FDM) and SNOWPACK, and force these (partly) 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. An evaluation using 75 snow temperature observations at 10 m depth and density profiles from 11 firn cores shows that output of both snow models is sufficiently realistic to warrant further analysis of firn characteristics. The models give comparable results: in 941 model grid points in either model, covering ∼28 000 km2, PFAs existed for at least 1 year in the simulated period, most notably in the western AP. At these locations, surface meltwater production typically exceeds 200 mmw.e.yr-1, with accumulation for most locations >1000mmw.e.yr-1. Most persistent and extensive are PFAs modelled on and around Wilkins Ice Shelf. Here, both meltwater production and accumulation rates are sufficiently high to sustain a PFA on 49 % of the ice shelf area in (up to) 100 % (depending on the model) of the years in the 1979–2016 period. Although this PFA presence is confirmed by recent observations, its extent in the models appears underestimated. Other notable PFA locations are Wordie Ice Shelf, an ice shelf that has almost completely disappeared in recent decades, and the relatively warm north-western side of mountain ranges in Palmer Land, where accumulation rates can be extremely high, and PFAs are formed frequently. PFAs are not necessarily more frequent in areas with the largest melt and accumulation rates, but they do grow larger and retain more meltwater, which could increase the likelihood of ice shelf hydrofracturing. We find that not only the magnitude of melt and accumulation is important but also the timing of precipitation events relative to melt events. Large accumulation events that occur in the months following an above-average summer melt event favour PFA formation in that year. 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 through the process of hydrofracturing in a similar way as supraglacial lakes do.

Expansion of Firn Aquifers in Southeast Greenland

“…However, drainage of firn‐aquifer water overall has the potential to create persistent subglacial channels through the winter due to continued high‐water pressure and to facilitate fast downstream channel growth during the summer melt season; this can ultimately dampen downglacier seasonal ice‐velocity fluctuations (Poinar et al., 2019). In addition, firn aquifers have been predicted near the grounding lines of many ice shelves of the rapidly changing Antarctic Peninsula (AP), including the former Prince Gustav, Wilkins, and Wordie Ice Shelves (van Wessem et al., 2021) and have been directly observed on the Wilkins Ice Shelf (Montgomery et al., 2020). Climate on the AP is similar to southeast Greenland, with high snow accumulation and high surface melt during the summer (Van Wessem et al., 2016; van Wessem et al., 2021) and even föhn‐induced melt in the winter season (Munneke et al., 2014).…”

“…In addition, firn aquifers have been predicted near the grounding lines of many ice shelves of the rapidly changing Antarctic Peninsula (AP), including the former Prince Gustav, Wilkins, and Wordie Ice Shelves (van Wessem et al., 2021) and have been directly observed on the Wilkins Ice Shelf (Montgomery et al., 2020). Climate on the AP is similar to southeast Greenland, with high snow accumulation and high surface melt during the summer (Van Wessem et al., 2016; van Wessem et al., 2021) and even föhn‐induced melt in the winter season (Munneke et al., 2014). With increasing precipitation rates (Thomas et al., 2008) and increasing atmospheric warming and surface melt (Abram et al., 2013; Turner et al., 2014), firn aquifers will be increasingly important to understand on the AP, as they may potentially accelerate the disintegration of ice shelves that buttress outlet glacier discharge to the oceans.…”

Climatology and Surface Impacts of Atmospheric Rivers on West Antarctica

“…In the second, we use observed snow height from the AMIGOS to force the firn model SNOWPACK to reconstruct accumulation during the AR event. SNOWPACK is a physicsbased, multi-layer firn model (Lehning et al, 2002b, a), which has been extensively applied in polar regions (Groot Zwaaftink et al, 2013;Steger et al, 2017;Van Wessem et al, 2021;Keenan et al, 2021). The model calculates fresh accumulation density as a function of meteorological conditions, particularly wind and the presence of drifting snow (Wever et al).…”

Introducing CRYOWRF v1.0: multiscale atmospheric flow simulations with advanced snow cover modelling

“…It was originally developed for avalanche forecasting and is in fact the operational model for this purpose in Switzerland. Since its original development nearly 2 decades ago, SNOWPACK has been continuously updated to include new physics and has been applied in different topics of cryospheric research, such as snow hydrology (Wever et al, 2015(Wever et al, , 2016aBrauchli et al, 2017), sea ice thermodynamics (Wever et al, 2020), snow-forest interaction (Gouttevin et al, 2015), ice-sheets mass balance and thermodynamics (Steger et al, 2017b, a;van Wessem et al, 2021;Keenan et al, 2021), and climate-change-induced impact assessments on snow and snow hydrology (Bavay et al, 2013(Bavay et al, , 2009Marty et al, 2017). In all the above applications, SNOWPACK has been forced either with meteorological measurement data or NWP/climate model outputs in an offline setting.…”

“…In spite of its ubiquitous importance in cryospheric regions, blow-ing snow models are not included in any of the participating models in CMIP6. There are implementations of blowing snow models in regional-scale climate models (RCMs) such as RACMO (van Wessem et al, 2018;Lenaerts et al, 2012), MAR (Amory et al, 2015, for polar regions), and Meso-NH (Vionnet et al, 2012, for alpine regions). Publicly available versions of WRF do not include any model of this important phenomenon (a recent effort to include a blowing snow model in WRF has been published by Luo et al, 2021. However, the model does not seem to be publicly available).…”