The concept of a positive feedback between ice flow and enhanced melt rates in a warmer climate fuelled the debate regarding the temporal and spatial controls on seasonal ice acceleration. Here we combine melt, basal water pressure and ice velocity data. Using 20 years of data covering the whole ablation area, we show that there is not a strong positive correlation between annual ice velocities and melt rates. Annual velocities even slightly decreased with increasing melt. Results also indicate that melt variations are most important for velocity variations in the upper ablation zone up to the equilibrium line altitude. During the extreme melt in 2012, a large velocity response near the equilibrium line was observed, highlighting the possibility of meltwater to have an impact even high on the ice sheet. This may lead to an increase of the annual ice velocity in the region above S9 and requires further monitoring.

This paper presents autonomous drifting snow observations performed on the Greenland Ice Sheet in the fall of 2012. High-frequency snow particle counter (SPC) observations at ~ 1 m above the surface provided drifting snow number fluxes and size distributions; these were combined with meteorological observations at six levels. We identify two types of drifting snow events: katabatic events are relatively cold and dry, with prevalent winds from the southeast, whereas synoptic events are short lived, warm and wet. Precipitating snow during synoptic events disturbs the drifting snow measurements. Output of the regional atmospheric climate model RACMO2, which includes the drifting snow routine PIEKTUK-B, agrees well with the observed near-surface climate at the site, as well as with the frequency and timing of drifting snow events. Direct comparisons with the SPC observations at 1 m reveal that the model overestimates the horizontal snow transport at this level, which can be related to an overestimation of saltation and the typical size of drifting snow particles.

1 Greenland 2 3 R.S.W. van de Wal, C.J.P.P. Smeets, W. Boot, M. Stoffelen, R. van Kampen, S. 4 Doyle, F. Wilhelms, M.R. van den Broeke, C.H. Reijmer, J. Oerlemans, A. 5 Hubbard 6 1:Institute for Marine and Atmospheric research Utrecht, Utrecht University, and The Netherlands. 7 2:Centre for Glaciology, Institute of Geography and Earth Sciences, Aberystwyth University, 8 Aberystwyth, UK. 9 3:Alfred Wegener Institute, Bremerhaven, Germany. 10 11 Abstract 12 13 The concept of a positive feedback between ice flow and enhanced melt rates in a 14 warmer climate fuelled the debate regarding the temporal and spatial controls on 15 seasonal ice acceleration. Here we combine melt, basal water pressure, and ice velocity 16 data. We show using twenty years of data covering the whole ablation area that there is 17 not a strong positive correlation between annual ice velocities and melt rates. Annual 18 velocities even slightly decreased with increasing melt. Results also indicate that melt 19 variations are most important for velocity variations in the upper ablation zone up to 20 the equilibrium line altitude. During the extreme melt in 2012 a large velocity response 21 near the equilibrium line was observed, highlighting the possibility of meltwater to 22 have an impact even high on the ice sheet. This may lead to an increase of the annual 23 ice velocity in the region above S9 and requires further monitoring. 24 25

Since February 2009, an automatic weather station (AWS) has been operating near Utsteinen Nunatak, north of the Sør Rondane Mountains, in Dronning Maud Land at the ascent to the East Antarctic Plateau. This paper gives an assessment of the meteorological conditions, radiative fluxes, and snow accumulation for the first 2 years of operation, 2009 to 2010, analyzed in terms of meteorological regimes. Three major meteorological regimes—cold katabatic, warm synoptic, and transitional synoptic—are identified using cluster analysis based on five parameters derived from the AWS measurements (wind speed, specific humidity, near‐surface temperature inversion, surface pressure, and incoming longwave flux indicative of cloud forcing). For its location, the relatively mild climate at Utsteinen can be explained by the high frequency of synoptic events (observed 41%–48% of the time), and a lack of drainage of cold air from the plateau due to mountain sheltering. During the cold katabatic regime, a strong surface cooling leads to a strong near‐surface temperature inversion buildup. A large difference in accumulation is recorded by the AWS for the first 2 years: 235 mm water equivalent in 2009 and 27 mm water equivalent in 2010. Several large accumulation events during the warm synoptic regime occurring mainly in winter were responsible for the majority of the accumulation in 2009. Mostly, small accumulation events occurred during 2010, frequently followed by snow removal. This interannual variability in snow accumulation at the site is related to the intensity of the local synoptic events as recorded by meteorological regime characteristics.

We present the design and first results from two experiments using a wireless subglacial sensor system (WiSe) that is able to transmit data through 2500 m thick ice. Energy consumption of the probes is minimized, enabling the transmission of data for at least 10 years. In July 2010 the first prototype of the system was used to measure subglacial pressure at the base and a temperature profile consisting of 23 probes in two 600 m deep holes at Russell Glacier, a land-terminating part of the West Greenland ice sheet near Kangerlussuaq. The time series of subglacial pressure show very good agreement between data from the WiSe system and the wired reference system. The wireless-measured temperature data were validated by comparison with the theoretical decrease of melting point with water pressure inside the water-filled hole directly after installation. To test the depth range of the WiSe system a second experiment using three different probe types and two different surface antennas was performed inside the 2537 m deep hole at NEEM. It is demonstrated that, with the proper combination of transmission power and surface antenna type, the WiSe system transmits data through 2500 m thick ice.

We present the design and first results from two experiments using a wireless subglacial sensor system (WiSe) that is able to transmit data through 2500 m thick ice. Energy consumption of the probes is minimized, enabling the transmission of data for at least 10 years. In July 2010 the first prototype of the system was used to measure subglacial pressure at the base and a temperature profile consisting of 23 probes in two 600 m deep holes at Russell Glacier, a land-terminating part of the West Greenland ice sheet near Kangerlussuaq. The time series of subglacial pressure show very good agreement between data from the WiSe system and the wired reference system. The wireless-measured temperature data were validated by comparison with the theoretical decrease of melting point with water pressure inside the water-filled hole directly after installation. To test the depth range of the WiSe system a second experiment using three different probe types and two different surface antennas was performed inside the 2537 m deep hole at NEEM. It is demonstrated that, with the proper combination of transmission power and surface antenna type, the WiSe system transmits data through 2500 m thick ice.

A 21-yr record is presented of surface mass balance measurements along the K-transect. The series covers the period 1990–2011. Data are available at eight sites along a transect over an altitude range of 380–1850 m at approximately 67° N in West Greenland. The surface mass balance gradient is on average 3.8 × 10−3 m w.e. m−1, and the mean equilibrium line altitude is 1553 m a.s.l. Only the lower three sites within 10 km of the margin up to an elevation of 700 m experience a significant increasing trend in the ablation over the entire period. Data are available at: doi:10.1594/PANGAEA.779181.

The Antarctic mass balance and the hydrological cycle of the entire planet are tightly linked together. Evaporation from the ocean surface in the tropical and middle latitudes, poleward moisture and energy transport, changes in the midlatitude atmospheric dynamics, cloud formation microphysics - all these processes determine the amount of precipitation in Antarctica. The main objective of our project is to improve the understanding of the atmospheric branch of the hydrological cycle of Antarctica covering the chain from evaporation/sublimation at the surface via cloud formation to snowfall. As there is a lack of on the clouds and precipitation processes in the Antarctic, the first goal is to establish a new database that can be used for local process studies and large-scale model evaluation. The base for our measurements is the new Belgian Antarctic station Princess Elisabeth (PE) built on the Utsteinen Ridge in Dronning Maud Land, East Antarctica (71 57’ S and 23 20’ E, 1400masl, 180km inland). Princess Elisabeth station is located in a nearly thousand kilometer wide data gap, where no long-term measurements of the surface mass balance have been done up to date and where regional climate models show large differences in snow accumulation estimates.

Snowmelt constitutes an important part of the surface energy and mass balance of the ice sheets of Greenland and Antarctica. In Greenland, the entire ice sheet experiences occasional melt, as indicated by thin, isolated ice lenses in firn cores drilled at the highest part of the ice sheet and supported by regional atmospheric climate models (Ettema et al., 2010). In Antarctica, melt is limited to the coastal areas, but is especially significant in the Antarctic Peninsula, where the melt season may last as long as three months (Tedesco and Monaghan, 2009). On both ice sheets, the largest fraction of the melt energy is invested in the melting of snow rather than ice. The reason is that the Greenland ablation zone is relatively narrow and constitutes less than 10% of the total surface area. In Antarctica, ablation areas form at locations where sublimation (not melt!) locally exceeds snowfall. These so-called blue ice areas constitute less than 1% of the total surface area and as a result, nearly all surface melt in Antarctica is due to snowmelt.

Two technical developments are presented: a new generation of AWS and a wireless subglacial measurement system. Both systems build on the experience of the IMAU in developing GPS systems (Den Ouden et al., 2010). Combining methods to minimize energy consumption and wireless communication form the basis of the new systems described here.