ALBERT

Description: Spatio-temporal patterns of climatic variability have effects on the environmental conditions of a given land territory and consequently determine the evolution of its productive activities. One of the most direct ways to evaluate this relationship is to measure the condition of the vegetation cover and land-use information. In southernmost South America there is a limited number of long-term studies on these matters, an incomplete network of weather stations and almost no database on ecosystems productivity. In the present work, we characterized the climate variability of the Magellan Region, southernmost Chilean Patagonia, for the last 34 years, studying key variables associated with one of its main economic sectors, sheep production, and evaluating the effect of extreme weather events on ecosystem productivity and sheep production. Our results show a marked multi-decadal character of the climatic variables, with a trend to more arid conditions for the last 8 years, together with an increase in the frequency of extreme weather events. Significant percentages of aboveground net primary productivity (ANPP) variance is explained by high precipitation, mesic temperatures, and low evapotranspiration. These conditions are, however, spatially distributed in the transition zone between deciduous forests and steppe and do not represent a general pattern for the entire region. Strong precipitation and wind velocity negatively affect lamb survival, while temperature and ANPP are positively correlated. The impact of extreme weather events on ANP and sheep production (SP) was in most of the cases significantly negative, with the exception of maximum temperature that correlated with an increase of ANPP, and droughts that showed a non-significant negative trend in ANPP. The examination of these relationships is urgent under the current scenario of climate change with the acceleration of the environmental trends here detected.

Description: Since recent drought events have already caused severe damage to trees and droughts in the near future are expected to occur even more frequently, this study investigated the response of forest ecosystems to changing climate conditions in the topographically complex region of Bavaria, southeast Germany. For this purpose, climate–growth relationships of important European deciduous and coniferous tree species were investigated over the past 50 years at three middle mountain ranges and corresponding basins. A response analysis between tree-ring width and climate variables was applied to detect modifications in tree responses comparing two 25-year periods at individual forest sites. Furthermore, tree responses to climatic extreme years and seasons were analyzed using a superposed epoch analysis. The results showed that Scots pine (Pinus sylvestris) proved to be the most vulnerable and least drought-resistant of all investigated tree species. Likewise, Norway spruce (Picea abies) and European beech (Fagus sylvatica) revealed a higher drought sensitivity over the past 25 years, even though an extended growing season partially improved tree growth at high-elevation sites. In conclusion, all studied tree species were affected by drought events, even at humid high-elevation sites. Correlations with daily climate variables confirmed that even short-term weather conditions could strongly influence trees’ radial growth. Tree responses to climate conditions have shifted significantly between past and present periods but vary considerably among sites and are generally stronger in humid regions than in already dry areas.

Description: We present a satellite-derived glacier inventory for the whole Patagonian Andes south of 45. 5°S and Tierra del Fuego including recent changes. Landsat TM/ETM+ and OLI satellite scenes were used to detect changes in the glacierized area between 1986, 2005 and 2016 for all of the 11,209 inventoried glaciers using a semi-automated procedure. Additionally we used geomorphological evidence, such as moraines and trimlines to determine the glacierized area during the Little Ice Age for almost 90% of the total glacierized area. Within the last ~150 years the glacierized area was reduced from 28,091 ± 890 km² to 22,636 ± 905 km², marking an absolute area loss of 5,455 ± 1,269 km² (19.4 ± 4.5%). For the whole study region, the annual area decrease was moderate until 1986 with 0.10 ± 0.04%/a. Afterwards the area reduction increased, reaching annual values of 0.33 ± 0.28%/a and 0.25 ± 0.50%/a for the periods of 1986-2005 and 2005-2016, respectively. There is a high variability of change rates throughout the Patagonian Andes. Small glaciers, especially in the north of the Northern Patagonian Icefield (NPI) and between the latter and the Southern Patagonian Icefield (SPI) had over all periods the highest rates of shrinkage, exceeding 0.92 ± 1.22%/a during 2005-2016. In the mountain range of the Cordillera Darwin (CD), and also accounting for small ice fields south of 52°S, highest rates of shrinkage occurred during 1986-2005, reaching values up to 0.45 ± 0.23%/a, but decreased during the 2005-2016 period. Across the Andean main crest, the eastern parts of the NPI, SPI and adjoined glaciers had in absolute values the highest area reduction exceeding 2,145 ± 486 km² since the LIA. Large calving glaciers show a smaller relative decrease rate compared to land-terminating glaciers but account for the most absolute area loss. In general, glacier shrinkage is dependent on latitude, the initial glacier area, the environment of the glacial tongue (calving or non-calving glaciers) and in parts by glacial aspect.

Description: The contribution to sea level rise from Patagonian icefields is one of the largest mass losses outside the large ice sheets of Antarctica and Greenland. However, only a few studies have provided large-scale assessments in a spatially detailed way to address the reaction of individual glaciers in Patagonia and hence to better understand and explain the underlying processes. In this work, we use repeat radar interferometric measurements of the German TerraSAR-X-Add-on for Digital Elevation Measurements (TanDEM-X) satellite constellation between 2011/12 and 2016 together with the digital elevation model from the Shuttle Radar Topography Mission (SRTM) in 2000 in order to derive surface elevation and mass changes of the Southern Patagonia Icefield (SPI). Our results reveal a mass loss rate of −11.84 ± 3.3 Gt- a−1 (corresponding to 0.033 ± 0.009 mm- a−1 sea level rise) for an area of 12573 km2 in the period 2000-2015/16. This equals a specific glacier mass balance of −0.941 ± 0.19 m w.e.- a−1 for the whole SPI. These values are comparable with previous estimates since the 1970s, but a magnitude larger than mass change rates reported since the Little Ice Age. The spatial pattern reveals that not all glaciers respond similarly to changes and that various factors need to be considered in order to explain the observed changes. Our multi-temporal coverage of the southern part of the SPI (south of 50.3° S) shows that the mean elevation change rates do not vary significantly over time below the equilibrium line. However, we see indications for more positive mass balances due to possible precipitation increase in 2014 and 2015. We conclude that bi-static radar interferometry is a suitable tool to accurately measure glacier volume and mass changes in frequently cloudy regions. We recommend regular repeat TanDEM-X acquisitions to be scheduled for the maximum summer melt extent in order to minimize the effects of radar signal penetration and to increase product quality.

Description: This data collection contains readings of accumulation stake along the approximately 800 km long traverse route Neumayer-Kottas-Kohnen, Dronning Maud Land, Antarctica. By comparing the readings of an individual stake in two different seasons the amount of surface accumulation (i.e. snow deposition) or erosion (e.g. from sublimation of wind scour) can be determined. Stake readings were conducted approximately every year starting from season 1995/1996 to 2005/2006 as part of the European Project for Ice Coring In Antarctica (EPICA). The readings were carried out by a dedicated two to three person team accompanying the traverse from Neumayer station to Kohnen station. The readings were performed by a simple measurement of the visible length of the stake above the snow surface. For tilted stakes, the vertical height above the surface as well as the length of the stake was measured. New stakes were deployed when less than about 1.5 m of the previous stake was visible or a stake was lost (e.g. from breaking off or falling over and finally get burried in snow). Consequently, at some locations more than one stake is visible for several years (e.g. when the average snow accumulation was rather low). In those cases all visible stakes were recorded at the same location of such a stake cluster and added to the table as Height_1, Height 2, Height 3). Positions were measured with a simple GPS with coarse acquisition accuracy (order of several meters to tens of meters), which is sufficiently accurate to separate different stake locations (usually 500 m apart and horizontal displacement smaller than about 150 m/a, with largest displacements on the Ekström ice shelf). In very few cases, empty lines originate from missing stakes and the required position. In very few cases, a second line with the same coordinate corresponds to the same location with a fourth stake deployed as a new stake. From Neumayer station to Kottas camp stakes were deployed at approximately a 500 m interval. As the spatial variation of accumulation on the polar plateau is smaller than in the lower foreland (in this case the Ritscherflya) the stake distances was increased to 1 km to several kilometers from Kottas camp onto the polar plateau to Kohnen station. Additional field comments made by observing personal were removed from the files. However, original field notes in notebooks are available from AWI's Archive for German Polar Research (Oerter et al., 2013). Although surface accumulation is still one of the major unknowns to determine the the total surface mass balance of the Antarctic ice sheet, especially under climate change, direct long-term observations of surface accumulation are still one of the major gaps in field observations (Eisen et al., 2008). This time series of stake readings provides the basis for calculation the change in accumulation in space and time (e.g. Rotschky et al., 2007). It is thus fundamental for a decade-long record of the spatio-temporal characteristics of surface accumulation, which can be put into context to meteorological and oceanographic changes in the region.