The effect of synoptic scale weather systems on sub‐surface soil temperatures in a diurnal frost environment: preliminary observations from sub‐antarctic marion island

Abstract

. Marion Island in the South Indian Ocean has a maritime climate dominated by diurnal frost processes in the landscape. We test the hypothesis that synoptic time‐scale measurements are essential in understanding the drivers of diurnal frost processes. Preliminary results from automated microclimate measurements in a polar desert habitat show that diurnal soil surface temperatures on Marion Island are influenced by a complex interaction of radiation balance, air mass circulation, cloud cover and snow. The passage of synoptic scale weather systems influences soil thermal characteristics through changes in dominance of the radiation budget. Soil frost on Marion appears to be dependent on clear skies, while synoptic weather systems affect the duration and intensity of soil frost processes and non‐radiative heat fluxes. Air circulation patterns at Marion Island influence diurnal scale temperature fluctuations and its direct and indirect interactions with ecosystem processes. The data suggest that in a maritime sub‐Antarctic environment the climatic drivers of soil frost occur at a finertemporal resolution than for seasonal and permafrost environments and needs to be measured at a diurnal time‐scale to be meaningful.

A preliminary synoptic assessment of soil frost on Marion Island and the possible consequences of climate change in a maritime sub-Antarctic environment

“…Recent preliminary results show that at the microscale diurnal soil surface temperatures on Marion Island are influenced by a complex interaction of radiation balance, air mass circulation, cloud cover and snow (Nel, Boelhouwers et al 2009). Effective nocturnal cooling to below freezing point has historically been reported to depend on clear, windless nights (Outcalt 1971) and soil frost on Marion Island also appears dependent on clear skies (Nel, Boelhouwers et al 2009), with frequencies ranging from 60 to over 200 days per year in a climate dominated by strong winds, cloud cover and high soil moisture values.…”

“…Effective nocturnal cooling to below freezing point has historically been reported to depend on clear, windless nights (Outcalt 1971) and soil frost on Marion Island also appears dependent on clear skies (Nel, Boelhouwers et al 2009), with frequencies ranging from 60 to over 200 days per year in a climate dominated by strong winds, cloud cover and high soil moisture values. Misty and overcast conditions are associated with maritime temperate air mass and westerly circulation.…”

“…S, 378 45? E) lies in the subAntarctic and has a hyper-maritime setting and a sensitive periglacial environment which is important in understanding climate/surface interactions as well as the climate change effects on ground thermal processes (Nel, Boelhouwers et al 2009;Nel, Van der Merwe et al 2009). The island is situated in the southern Indian Ocean and the synoptic climate is characterized by sequences of mid-latitude depressions (cyclones), the passages of frontal systems and the influences of anticyclones (Vowinckel 1954;Le Roux 2008).…”

“…In contrast, diurnal ground frost dominates the sub-polar region of the Antarctic, and the time scale at which climate drivers affect the ground frost conditions is on the order of hours to days (Nel, Boelhoewers et al 2009), rather than seasonal or annual. At the diurnal time scale synoptic weather conditions control the temporal variability in ground temperature (Nel, Boelhouwers et al 2009;Nel, Van der Merwe et al 2009), which is superimposed on the seasonal shift in ground energy budget (Boelhouwers et al 2008). …”

Wind Distortion in Alpine and Subantarctic Plants is Constant among Life Forms but does not Necessarily Reflect Prevailing Wind Direction

“…In contrast to the leeward migration typically observed in feldmark plants, Boelhouwers et al (2003) reported A. selago cushions migrating toward the prevailing wind as a result of decay of the cushions on the leeward side where needle ice forms. On Marion Island, frost events are predominantly associated with southwesterly airflows (Nel et al, 2009). Macquarie Island is likely to experience a similar regime given the similarities in synoptic weather patterns and soil temperatures between it and Marion Island, and thus windblown ice is likely associated with southwesterly winds.…”