ALBERT

Description: This study assesses the response on ice dynamics of Petermann Glacier, a major outlet glacier in northern Greenland, to the 2012 and a possible future calving event. So far Petermann Glacier has been believed to be dynamically stable as another large calving event in 2010 had no significant impact on flow velocity or grounding line retreat. By analyzing a time series of remotely sensed surface velocities, we find an average acceleration of 10% between winter 2011/2012 and winter 2016/2017. This increase in surface velocity is not linear but can be separated into two parts, starting in 2012 and 2016 respectively. By conducting modelling experiments, we show that the first speed-up can be directly connected to the 2012 calving event, while the second speed-up is not captured. However, on recent remote sensing imagery newly developing fractures are clearly visible ~12,km upstream from the terminus, propagating from the eastern fjord wall to the center of the ice tongue, indicating a possible future calving event. By including these fracture zones as a new terminus position in the modelling domain we are able to reproduce the second speed-up, suggesting that surface velocities remain on the 2016/2017 level after the anticipated calving event. This indicates that, from a dynamical point of view, the terminus region has already detached from the main ice tongue.

Description: This dataset contains outline polygons and water area time series of supraglacial lakes at the two main glacier systems of the Northeast Greenland Ice Stream, Nioghalvfjerdsbræ (also known as 79°N Glacier) and Zachariæ Isstrøm. The dataset was derived from Polarimetric Synthetic Aperture Radar observations (PolSAR) of the ESA satellites Sentinel-1A and Sentinel-1B during 2017-2020 and consists of a polygon file defining the lake outline definitions, a NetCDF file containing time series of water area and further parameters for each lake and a PDF with further details to the other files content. It was created as part of the European Union's Horizon 2020 research and innovation programme via project iCUPE (Integrative and Comprehensive Understanding on Polar Environments).

Description: Ice complex deposits are characteristic, ice-rich formations in northern East Siberia and represent an important part in the arctic carbon pool. Recently, these late Quaternary deposits are the objective of numerous investigations typically relying on outcrop and borehole data. Many of these studies can benefit from a 3D structural model of the subsurface for upscaling their observations or for constraining estimations of inventories, such as the local carbon stock. We have addressed this problem of structural imaging by 3D ground-penetrating radar (GPR), which, in permafrost studies, has been primarily used for 2D profiling. We have used a 3D kinematic GPR surveying strategy at a field site located in the New Siberian Archipelago on top of an ice complex. After applying a 3D GPR processing sequence, we were able to trace two horizons at depths below 20 m. Taking available borehole and outcrop data into account, we have interpreted these two features as interfaces of major lithologic units and derived a 3D cryostratigraphic model of the subsurface. Our data example demonstrated that a 3D surveying and processing strategy was crucial at our field site and showed the potential of 3D GPR to image geologic structures in complex ice-rich permafrost landscapes.

Description: The drainage divides of ice sheets separate the overall glaciated area into multiple sectors. These drainage basins are essential for partitioning mass changes of the ice sheet, as they specify the area over which basin specific measurements are integrated. The delineation of drainage basins on ice sheets is challenging due to their gentle slopes accompanied by local terrain disturbances and complex patterns of ice movement. Until now, in Greenland the basins have been mostly delineated along the major ice divides, which results in large drainage sectors containing multiple outlet glaciers. However, when focusing on measuring glaciological parameters of individual outlet glaciers, more detailed drainage basin delineations are needed. Here we present for the first time a detailed and fully traceable approach that combines ice sheet wide velocity measurements by Sentinel-1 and the high resolution TanDEM-X global DEM to derive individual glacier drainage basins. We delineated catchments for the Northeast Greenland Ice Sheet with a modified watershed algorithm and present results for 31 drainage basins. Even though validation of drainage basins remains a difficult task, we estimated basin probabilities from Monte-Carlo experiments and applied the method to a variety of different ice velocity and DEM datasets finding discrepancies of up to 16% in the extent of catchment areas. The proposed approach has the potential to produce drainage areas for the entirety of the Greenland and Antarctic ice sheets.

Description: Lake Ohrid (Macedonia, Albania) is thought to be more than 1.2 million years old and host more than 300 endemic species. As a target of the International Continental scientific Drilling Program (ICDP), a successful deep drilling campaign was carried out within the scope of the Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) project in 2013. Here, we present lithological, sedimentological, and (bio-)geochemical data from the upper 247.8m composite depth of the overall 569m long DEEP site sediment succession from the central part of the lake. According to an age model, which is based on 11 tephra layers (first-order tie points) and on tuning of bio-geochemical proxy data to orbital parameters (second-order tie points), the analyzed sediment sequence covers the last 637 kyr. The DEEP site sediment succession consists of hemipelagic sediments, which are interspersed by several tephra layers and infrequent, thin (〈 5 cm) mass wasting deposits. The hemipelagic sediments can be classified into three different lithotypes. Lithotype 1 and 2 deposits comprise calcareous and slightly calcareous silty clay and are predominantly attributed to interglacial periods with high primary productivity in the lake during summer and reduced mixing during winter. The data suggest that high ion and nutrient concentrations in the lake water promoted calcite precipitation and diatom growth in the epilimnion during MIS15, 13, and 5. Following a strong primary productivity, highest interglacial temperatures can be reported for marine isotope stages (MIS) 11 and 5, whereas MIS15, 13, 9, and 7 were comparably cooler. Lithotype 3 deposits consist of clastic, silty clayey material and predominantly represent glacial periods with low primary productivity during summer and longer and intensified mixing during winter. The data imply that the most severe glacial conditions at Lake Ohrid persisted during MIS16, 12, 10, and 6, whereas somewhat warmer temperatures can be inferred for MIS14, 8, 4, and 2. Interglacial-like conditions occurred during parts of MIS14 and 8.

Description: Major and trace element composition as well as Sm-Nd isotopes of whole-rock samples and clay fractions (〈2 µm) of bentonite layers and U-Pb ages of detrital zircons from the Paleogene Basilika Formation (Svalbard) and Mount Lawson Formation (Ellesmere Island).

Description: The sediment succession of Lake Emanda in the Yana Highlands was investigated to reconstruct the regional late Quaternary climate and environmental history. Hydro-acoustic data obtained during a field campaign in 2017 show laminated sediments in the north-western and deepest (up to ~15 m) part of the lake, where a ~6-m-long sediment core (Co1412, latitude 65°17.6490N, longitude 135°45.5540E) was retrieved. The sediment core was studied with a multi-proxy approach including sedimentological and geochemical analyses. The chronology of Co1412 is based on 14C AMS dating on plant fragments from the upper 4.65 m and by extrapolation, suggesting a basal age of c. 57 cal. ka BP.Biogeochemistry analysis of sediment Co1412: TOC=total organic carbon (%), TN=total nitrogen (%), TOC/TN (atomic), TS=total sulphur (%), TIC=total inorganic carbon (%) data of sediment Co1412 against composite depth (cm) and age (cal. a BP).