Paul C. J. P. Smeets's research while affiliated with Utrecht University and other places

... Strong surface warming started around the year 1996 ( Figure 3b). Indeed, the temperature at 10 m depth shows a time evolution with recent warming closely resembling the 10 m temperatures described by Vandecrux et al. (2023). The firn at the bottom of the domain (∼26 m depth), however, originated in the colder years around 1970. ...

... R24 compares well to T2m observations (Fig. 9b) of the AntAWS observational data set (Wang et al., 2023), with stations being situated all over the AIS (locations shown in Fig. 1b). The determination coefficient is high and the fit line is close to the 1-on-1 line, in particular for cold conditions (T2m lower than -40°C). ...

... When available, near-surface meteorological observations are subjected to correction and homogenization to reduce first-order measurement errors, for instance associated with riming and/or station tilt affecting the measurement of shortwave radiation [19,66,70,71]. Validity of surface layer similarity is usually assumed in combination with a bulk gradient approach to quantify the turbulent fluxes, SHF and LHF, which requires assumptions about the surface aerodynamic roughness length [72]. Although over both ice sheets the surface aerodynamic roughness length can differ by several orders of magnitude in space and time [73][74][75], its value is usually prescribed as constant or used as tuning parameter [32]. ...

... The strong warming signal has disappeared in the Antarctic Peninsula since the late 1990s, which is related to the strengthening of mid-latitude jets [27]. In addition, the warming sign dominated East Antarctica in the austral spring, and Antarctic amplification existed in the austral spring for the period 1979-2019 [28][29][30]. Generally, the Arctic and the Third Pole have experienced obvious warming, while Antarctic temperature decreased in the second half of the 20th century, and the variations have reversed in recent years. ...

... The K-transect has been maintained by Utrecht University since 1990, the latter two networks have been merged in 2021 by the Geological Survey of Denmark and Greenland (GEUS). On the AIS, although the absolute number of AWS with~150 is substantial [68], the number of such SEB-enabled AWS in melt regions remains small (< 20) and is only slowly increasing [24,69]. When available, near-surface meteorological observations are subjected to correction and homogenization to reduce first-order measurement errors, for instance associated with riming and/or station tilt affecting the measurement of shortwave radiation [19,66,70,71]. ...

... Antarctica climate and ice sheet altitude evolution have been measured for 4 decades based on remote sensing and show an increasing mass loss in Wilkes Land (Rignot et al., 2019). These reconstructions require calibrations or evaluation with ground-based measurements, but weather stations and direct observations of surface mass balance are sparse (Favier et al., 2013;Wang et al., 2021). Global reanalysis data are suitable for studying climate variability, but these products have only been reliable in the data-scarce Antarctic region since 1979, when they began assimilating satellite data (Marshall et al., 2022). ...

... However, classical ORS, such as airborne and spaceborne sensors, have spatial and temporal resolution limitations and high operational costs, although images are usually free for users. These limitations can be solved with the use of Unmanned Aerial Vehicle & Remote Sensing (UAV-RS) technologies (Matese et al., 2015;Riveros-Burgos et al., 2021), which are widely used in forestry (Giannetti et al., 2020;Guerra-Hernández et al., 2019), agronomy (Jurado et al., 2020;Rallo et al., 2020;Viera-Torres et al., 2020), climate change research (van Tiggelen et al., 2021), natural risk management (Filkov et al., 2021;Weber et al., 2020), and soil science (Garg et al., 2020;Hout et al., 2020). UAV-RS has been used in soil pollution studies (Choe et al., 2008;Jia et al., 2021a) and, when compared with conventional methodologies, it is faster, less expensive, and non-invasive (Chabrillat et al., 2019). ...

... We choose to use MERRA-2 since it is publicly available, regularly updated and released, and spans a temporal window that captures recent climate change (Fig. A2). Regional climate models are not always widely available or regularly updated, and no single reanalysis clearly outperforms others over the GrIS (Zhang et al., 2021). Additionally, our focus is comparing two firn 95 models with the same forcing in order to isolate model differences. ...

... The underlying assumptions of the EC method are steady-state conditions during the measurement integration interval, in particular, a stationary, horizontal homogeneity of flow, and well-developed turbulence (Foken, 2021). The eddy-resolving EC method is a good alternative for observing the humidity flux in the accumulation zone of the GrIS, with commonly smaller errors under the prevailing neutral to slightly stable conditions compared to the bulk method, and it has been successfully used to estimate turbulent fluxes in Greenland in previous studies (Van Tiggelen et al., 2020;Miller et al., 2017). ...

... The ice speed-up from melt events can be larger in the late melt-season, when decreasing surface melt and ice creep cause the efficiency of the subglacial drainage system to decrease, making it susceptible to pressurization through minor variations in runoff (Fudge et al., 2009;Nanni et al., 2023). At this time of year, pulses of runoff are most frequently caused by rainfall and enhanced melt from atmospheric river events and cyclonic weather systems (Ballinger et al., 2019;Doyle et al., 2015) which are predicted to increase in frequency and intensity (Mattingly et al., 2018;Schuenemann & Cassano, 2010;Zhang et al., 2013). Therefore, associated transient speed-up events have been highlighted as a potential mechanism for increased mass loss over the coming decades (Bartholomaus et al., 2008;Doyle et al., 2015;Schmid et al., 2023;Schoof, 2010). ...