ALBERT

Description: To reconstruct palaeoclimate and palaeonvironmental conditions in the Northeast Siberian Arctic, we studied late Quaternary permafrost at the Oyogos Yar coast (Dmitry Laptev Strait). New infrared stimulated luminescence ages for distinctive floodplain deposits of the Kuchchugui Suite (112.5±9.6 kyr) and thermokarst-lake deposits of the Krest Yuryakh Suite (102.4±9.7 kyr), respectively, provide new substantial geochronological data and shed light on the landscape history of the Dmitry Laptev Strait region during the Marine Isotope Stage (MIS) 5. Ground ice stable-isotope data are presented together with cryolithological information for eight cryostratigraphic units and are complemented by data from nearby Bol'shoy Lyakhovsky Island. Our combined record of ice-wedge stable isotopes as proxy for past winter climate conditions covers about 200 thousand years and is supplemented by stable isotopes of pore and segregated ice which reflect annual climate conditions overprinted by freezing processes. Our ice wedge stable-isotope data indicate substantial variations in Northeast Siberian Arctic winter climate conditions during the late Quaternary, in particular between Glacial and Interglacial but also over the last millennia to centuries. Stable isotope values of Ice Complex ice wedges indicate cold to very cold winter temperatures about 200 kyr ago (MIS7), very cold winter conditions about 100 kyr ago (MIS5), very cold to moderate winter conditions between about 60 and 30 kyr ago, and extremely cold winter temperatures during the Last Glacial Maximum (MIS2). Much warmer winter conditions are reflected by extensive thermokarst development during the MIS5c and by Holocene ice-wedge stable-isotopes. Modern ice-wedge stable isotopes are most enriched and testify the recent winter warming in the Arctic. Hence, ice-wedge based reconstructions of changes in winter climate conditions add substantial information to those derived from paleoecological proxies stored in permafrost and allow for distinguishing between seasonal trends of past climate dynamics. Future progress in ice-wedge dating and an improved temporal resolution of ice-wedge derived climate information may help to fully explore the palaeoclimatic potential of ice wedges.

Description: Geospatial Data: - Watershed delineation based on hydrology toolbox in ArcGIS (ESRI, version 10.3) - Mapped disturbances based on aerial photographs from 1952 and 1970 (for Ice Creek East, Ice Creek West and Eastern Gully only) and satellite imagery from 2011 (GeoEye-1) and 2015 (WorldView2). Note that no disturbances were found in Slump D creek. Hydrology Data: - Manual flow measurements with the Flo-Mate 2000 Flow Meter different streams on Herschel Island - Runoff data in Ice Creek East - continuous measurements - Runoff data in Ice Creek West - continuous measurements Hydrochemistry Data: - hydrochemistry data of 2016 including pH, conductivity, turbidity, stable water isotopes, solutes, POC and DOC More details on the methods can be found in the accompanying manuscript.

Description: Subseabed CO2 storage is considered a future climate change mitigation technology. We investigated the ecological consequences of CO2 leakage for a marine benthic ecosystem. For the first time with a multidisciplinary integrated study, we tested hypotheses derived from a meta-analysis of previous experimental and in situ high-CO2 impact studies. For this, we compared ecological functions of naturally CO2-vented seafloor off the Mediterranean island Panarea (Tyrrhenian Sea, Italy) to those of nonvented sands, with a focus on biogeochemical processes and microbial and faunal community composition. High CO2 fluxes (up to 4 to 7 mol CO2 m−2 hour−1) dissolved all sedimentary carbonate, and comigration of silicate and iron led to local increases of microphytobenthos productivity (+450%) and standing stocks (+300%). Despite the higher food availability, faunal biomass (−80%) and trophic diversity were substantially lower compared to those at the reference site. Bacterial communities were also structurally and functionally affected, most notably in the composition of heterotrophs and microbial sulfate reduction rates (−90%). The observed ecological effects of CO2 leakage on submarine sands were reproduced with medium-term transplant experiments. This study assesses indicators of environmental impact by CO2 leakage and finds that community compositions and important ecological functions are permanently altered under high CO2.

Description: Sandy communities were exposed to six different seawater pCO2 regimes for a total of three months (17.12.2011–06.03.2012) in a climate - controlled room. Six header tanks were continuously supplied with filtered seawater from Kiel Fjord, each one connected to six experimental units (EU) ensuring continuous seawater supply. Each EU consisted of a round plastic container with a volume of 12.5 L containing ca. 9.5 L of sediment and an overlying water column of ca. 3 L. The lower 10 cm of the sediment consisted of sieved sand taken from a local beach (Kiel, Falckenstein: 54°23,66 N; 10°11.56 E) while the upper 10 cm consisted of surface sediment from the station at which the experimental animals were sampled to resemble natural conditions as well as to provide naturally occurring microbial and meiofauna communities. Bivalves and sediment were sampled in Kiel Fjord at Falckenstein with a Van Veen grab in 1–2 m depth and kept in holding basins at 9 °C before being placed in EUs. Numbers per EU simulated a natural size distribution: 5 M. arenaria (size classes: 0.5–1 cm: 2 animals; 1–1.5 cm: 2 animals; 2–2.5 cm: 1 animal), 1 M. balthica, and 40 C. edule (size classes: 0–0.5 cm: 3 animals; 0.5–1 cm: 18 animals; 1–1.5 cm: 11 animals; 1.5–2 cm: 7 animals; 2–2.5 cm: 1 animal). Small gastropods (exclusively Hydrobia spp.) were abundant with ~10 individuals per EU. Due to their small size (〈 0.5 mm) they were randomly distributed within all EUs with the sieved sediment. Due to the natural low diversity of the Baltic, the density of other macrofauna individuals was 〈 1 individuals per m². These low abundant species (e.g. nereid polychaetes, pharid bivalve species) were excluded from the experiment. The EUs were kept in a seawater flow-through system for two weeks under control conditions prior to the experiment to allow proper acclimatization of biogeochemistry and the faunal community. Seawater pH was maintained in the header tanks using a pH feedback system (IKS Aquastar, iksComput- ersysteme GmbH, Karlsbad, Germany). Treatment levels were achieved through continuous addition of acidified water from the header tanks into the overlaying seawater of each EU and included levels of 900 µatm (control, pH 7.8 NBS scale), 1,500 µatm (pH 7.7), 2,900 µatm (pH 7.4), 6,600 µatm (pH 7.0), 12,800 µatm (pH 6.7), and 24,400 µatm (pH 6.4). 900 µatm was used as a control due to the high background pCO2 in Kiel Fjord. To support the bivalve nutritional needs unicellular algae (Rhodomonas sp.) were cultured and added continuously into the header tanks via a peristaltic pump, thus maintaining a stable concentration of 3,500–4,000 cells ml−1 within header tanks. A flow rate of 100 ml min−1 was provided to each EU from the respective header tank via gravity feed. Throughout the experiment, pH, salinity, temperature, and flow rate were measured daily in each replicate. Salinity and temperature fluctuated in accordance with naturally occurring changes in Kiel Fjord seawater (14.6–20.5 psu and 4.3–8.9 °C, respectively). Light conditions were similar for all EUs. Dead animals were removed daily and behaviour of bivalves (presence/absence on the sediment surface) was noted every other day starting in the third experimental week. Carbonate chemistry and algae concentration in the EUs were measured weekly. Dissolved inorganic carbon (CT) was measured using an Automated Infrared Inorganic Carbon Analyzer (AIRICA, Marianda, Kiel, Germany). Seawater chemistry (pCO2 and calcium carbonate saturation state) was then calculated according to the guide to best practices for ocean CO2 measurements, using CO2SYS57 with pH (NBS scale) and CT, temperature, salinity, and first and second dissociation constants of carbonic acid in seawater.

Description: Ground ice and sedimentary records of a pingo exposure reveal insights into Holocene permafrost, landscape and climate dynamics. Early to mid‐Holocene thermokarst lake deposits contain rich floral and faunal paleoassemblages, which indicate lake shrinkage and decreasing summer temperatures (chironomid‐based TJuly) from 10.5 to 3.5 cal kyr BP with the warmest period between 10.5 and 8 cal kyr BP. Talik refreezing and pingo growth started about 3.5 cal kyr BP after disappearance of the lake. The isotopic composition of the pingo ice (δ18O − 17.1 ± 0.6‰, δD −144.5 ± 3.4‰, slope 5.85, deuterium excess −7.7± 1.5‰) point to the initial stage of closed‐system freezing captured in the record. A differing isotopic composition within the massive ice body was found (δ18O − 21.3 ± 1.4‰, δD −165 ± 11.5‰, slope 8.13, deuterium excess 4.9± 3.2‰), probably related to the infill of dilation cracks by surface water with quasi‐meteoric signature. Currently inactive syngenetic ice wedges formed in the thermokarst basin after lake drainage. The pingo preserves traces of permafrost response to climate variations in terms of ground‐ice degradation (thermokarst) during the early and mid‐Holocene, and aggradation (wedge‐ice and pingo‐ice growth) during the late Holocene.

Description: Stable water isotope signature measured from ice wedges in the Lena Delta, Bykovsky Peninsula. Samples were taken during espedition Lena 2000.