Active layer and permafrost thermal regime in a patterned ground soil in Maritime Antarctica, and relationship with climate variability models

Permafrost and active layer studies are important to understand and predict regional climate changes. The objectives of this work were: i) to characterize the soil thermal regime (active layer thickness and permafrost formation) and its interannual variability and ii) to evaluate the influence of different climate variability modes to the observed soil thermal regime in a patterned ground soil in Maritime Antarctica. The study was carried out at Keller Peninsula, King George Island, Maritime Antarctica. Six soil temperatures probes were installed at different depths (10, 30 and 80 cm) in the polygon center (Tc) and border (Tb) of a patterned ground soil. We applied cross-correlation analysis and standardized series were related to the Antarctic Oscillation Index (AAO). The estimated active layer thickness was approximately 0.75 cm in the polygon border and 0.64 cm in the center, indicating the presence of permafrost (within 80 cm). Results indicate that summer and winter temperatures are becoming colder and warmer, respectively. Considering similar active layer thickness, the polygon border presented greater thawing days, resulting in greater vulnerability to warming, cooling faster than the center, due to its lower volumetric heat capacity (Cs). Cross-correlation analysis indicated statistically significant delay of 1 day (at 10 cm depth) in the polygon center, and 5 days (at 80 cm depth) for the thermal response between atmosphere and soil. Air temperature showed a delay of 5 months with the climate variability models. The influence of southern winds from high latitudes, in the south facing slopes, favored freeze in the upper soil layers, and also contributed to keep permafrost closer to the surface. The observed cooling trend is linked to the regional climate variability modes influenced by atmospheric circulation, although longer monitoring period is required to reach a more precise scenario

Geospatial variability of soil CO2–C exchange in the main terrestrial ecosystems of Keller Peninsula, Maritime Antarctica

Soils and vegetation play an important role in the carbon exchange in Maritime Antarctica but little is known on the spatial variability of carbon processes in Antarctic terrestrial environments. The objective of the current study was to investigate (i) the soil development and (ii) spatial variability of ecosystem respiration (ER), net ecosystem CO2 exchange (NEE), gross primary production (GPP), soil temperature (ST) and soil moisture (SM) under four distinct vegetation types and a bare soil in Keller Peninsula, King George Island, Maritime Antarctica, as follows: site 1: moss-turf community; site 2: moss-carpet community; site 3: phanerogamic antarctic community; site 4: moss-carpet community (predominantly colonized by Sanionia uncinata); site 5: bare soil. Soils were sampled at different layers. A regular 40-point (5 × 8 m) grid, with a minimum separation distance of 1 m, was installed at each site to quantify the spatial variability of carbon exchange, soil moisture and temperature. Vegetation characteristics showed closer relation with soil development across the studied sites. ER reached 2.26 μmol CO2 m− 2 s− 1 in site 3, where ST was higher (7.53 °C). A greater sink effect was revealed in site 4 (net uptake of 1.54 μmol CO2 m− 2 s− 1) associated with higher SM (0.32 m3 m− 3). Spherical models were fitted to describe all experimental semivariograms. Results indicate that ST and SM are directly related to the spatial variability of CO2 exchange. Heterogeneous vegetation patches showed smaller range values. Overall, poorly drained terrestrial ecosystems act as CO2 sink. Conversely, where ER is more pronounced, they are associated with intense soil carbon mineralization. The formations of new ice-free areas, depending on the local soil drainage condition, have an important effect on CO2 exchange. With increasing ice/snow melting, and resulting widespread waterlogging, increasing CO2 sink in terrestrial ecosystems is expected for Maritime Antarctica

Geospatial variability of soil CO2–C exchange in the main terrestrial ecosystems of Keller Peninsula, Maritime Antarctica

Soils and vegetation play an important role in the carbon exchange in Maritime Antarctica but little is known on the spatial variability of carbon processes in Antarctic terrestrial environments. The objective of the current study was to investigate (i) the soil development and (ii) spatial variability of ecosystem respiration (ER), net ecosystem CO2 exchange (NEE), gross primary production (GPP), soil temperature (ST) and soil moisture (SM) under four distinct vegetation types and a bare soil in Keller Peninsula, King George Island, Maritime Antarctica, as follows: site 1: moss-turf community; site 2: moss-carpet community; site 3: phanerogamic antarctic community; site 4: moss-carpet community (predominantly colonized by Sanionia uncinata); site 5: bare soil. Soils were sampled at different layers. A regular 40-point (5 × 8 m) grid, with a minimum separation distance of 1 m, was installed at each site to quantify the spatial variability of carbon exchange, soil moisture and temperature. Vegetation characteristics showed closer relation with soil development across the studied sites. ER reached 2.26 μmol CO2 m− 2 s− 1 in site 3, where ST was higher (7.53 °C). A greater sink effect was revealed in site 4 (net uptake of 1.54 μmol CO2 m− 2 s− 1) associated with higher SM (0.32 m3 m− 3). Spherical models were fitted to describe all experimental semivariograms. Results indicate that ST and SM are directly related to the spatial variability of CO2 exchange. Heterogeneous vegetation patches showed smaller range values. Overall, poorly drained terrestrial ecosystems act as CO2 sink. Conversely, where ER is more pronounced, they are associated with intense soil carbon mineralization. The formations of new ice-free areas, depending on the local soil drainage condition, have an important effect on CO2 exchange. With increasing ice/snow melting, and resulting widespread waterlogging, increasing CO2 sink in terrestrial ecosystems is expected for Maritime Antarctica