Local climate of Zachary glacier, North East Greenland

In August 2016, two automatic weather stations (AWS) were placed on Zachary glacier, North East Greenland. They were installed in support of a project investigating the surface mass balance, ice velocity and calving conditions of Zachary glacier. The stations are full energy balance stations, i.e. they measure all parameters (air temperature, wind speed, relative humidity, air pressure, and short and long wave incoming and outgoing radiation) necessary to derive the full surface energy balance. In addition, the stations are equipped with a sonic height ranger in combination with a draw wire to measure snow accumulation and ice melt, respectively, and a GPS to monitor glacier velocity. These stations provide insight in the local climate of north east Greenland, a region for which only limited in situ data is available.

The AWS were located initially at ~145 m a.s.l., about 13 km from the glacier front (AWS23), and at  ~535 m a.s.l., about 35 km from the glacier front (AWS22). Both are moving reasonably fast (0.7 – 1.7 km/yr) towards the front, which has an impact on observed variables mainly since station elevation decreases, although changing (surrounding) topography impacts wind and radiation observations as well. Results show that both sites exhibit a strong katabatic signature, with directional constancies around 0.9, and wind speeds in winter being twice as strong as in summer. Temperature difference between the sites reflect the height difference, and is smaller in summer due to the melting surface impacting the near surface temperature. The lapse rate increases from ~0.5 °C/100 m in summer to ~0.7°C/100 m in the other seasons. The lower station, AWS23, is located in the ablation zone and has experienced on average 2.1 m ice melt over the past 3 years. At the higher station the mass budget appears to be in balance over this period.

The 3.5 years of available station data is compared with regional climate model RACMO2.3p2 output (5.5 km resolution), where monthly averaged data from the grid point nearest to the average station location is used. Initial differences in surface pressure reflect a difference in model grid height and station elevation (stations being located at lower elevation), while an increase in the absolute difference reflects the fast movement of the glacier transporting the AWS to lower elevations (30 and 70 m lowering for AWS22 and 23 respectively). The model overestimates temperature at AWS22 (1.3 °C), and wind speeds are too high at both sites.