| Popis |
The ice-free areas in Antarctica form less than 1 % of it; however, they are predicted to enlarge, especially in the Antarctic Peninsula (AP) Region. Different characteristics of the bare ground, such as much lower albedo in summer, change the energy distribution and so the surface energy budget of ice-free areas compared with ice-covered surfaces. Summer surface energy budget of non-glaciated areas has been examined in the South Shetland Islands on the western side of the AP (Prosek et al., 2000; Choi et al., 2008), but the energy fluxes of ice-free areas on the eastern side of the AP remain unknown. Consequently, the surface energy budget of the northern part of James Ross Island (Antarctic Peninsula Region) was measured during January–March 2018. The measurement set was installed at 10 m a. s. l. on a marine terrace in the northern part of the Ulu Peninsula. Net radiometer, eddy-covariance technique and heat flux plate method (Foken, 2008) were used to derive radiation balance components, sensible and ground heat fluxes, respectively. Furthermore, latent heat flux was modelled as in Langer et al. (2011). Net radiation stayed positive almost throughout the whole measurement time with the shortwave downward radiation being the most important and variable component. Four episodes of more extensive snow cover (daily mean albedo > 0.4) were observed, effectively reducing the daily mean net shortwave radiation by 75 %. Immense cloud cover increased daily mean downward longwave radiation by as much as 50 Wm-2 in the daily means, yet in result, the clouds acted to cool the surface. Sensible and latent heat fluxes were of comparable size, the magnitude of daily mean ground heat flux values was, however, about three times less than the other two fluxes. Daily mean latent heat flux was almost always positive, indicating evaporation/sublimation dominated during the period of measurement. Most of the energy gained from radiation was transformed into sensible heat flux, which, however, was negative a few times in the daily mean values. Daily mean ground heat flux often switched from positive to negative, resulting in mean value during the measurement period close to zero. Ground temperature down to 50-cm level reacted to changes in surface energy balance, especially to net radiation and ground heat flux.
|
