Beschreibung: Soils and other unconsolidated deposits in the northern circumpolar permafrost region store large amounts of soil organic carbon (SOC). This SOC is potentially vulnerable to remobilization following soil warming and permafrost thaw, but stock estimates are poorly constrained and quantitative error estimates were lacking. This study presents revised estimates of the permafrost SOC pool, including quantitative uncertainty estimates, in the 0–3 m depth range in soils as well as for deeper sediments (〉3 m) in deltaic deposits of major rivers and in the Yedoma region of Siberia and Alaska. The revised estimates are based on significantly larger databases compared to previous studies. Compared to previous studies, the number of individual sites/pedons has increased by a factor ×8–11 for soils in the 1–3 m depth range,, a factor ×8 for deltaic alluvium and a factor ×5 for Yedoma region deposits. Upscaled based on regional soil maps, estimated permafrost region SOC stocks are 217 ± 15 and 472 ± 34 Pg for the 0–0.3 m and 0–1 m soil depths, respectively (±95% confidence intervals). Depending on the regional subdivision used to upscale 1–3 m soils (following physiography or continents), estimated 0–3 m SOC storage is 1034 ± 183 Pg or 1104 ± 133 Pg. Of this, 34 ± 16 Pg C is stored in thin soils of the High Arctic. Based on generalised calculations, storage of SOC in deep deltaic alluvium (〉3 m to ≤60 m depth) of major Arctic rivers is estimated to 91 ± 39 Pg (of which 69 ± 34 Pg is in permafrost). In the Yedoma region, estimated 〉3 m SOC stocks are 178 +140/−146 Pg, of which 74 +54/−57 Pg is stored in intact, frozen Yedoma (late Pleistocene ice- and organic-rich silty sediments) with the remainder in refrozen thermokarst deposits (±16/84th percentiles of bootstrapped estimates). A total estimated mean storage for the permafrost region of ca. 1300–1370 Pg with an uncertainty range of 930–1690 Pg encompasses the combined revised estimates. Of this, ≤819–836 Pg is perennially frozen. While some components of the revised SOC stocks are similar in magnitude to those previously reported for this region, there are also substantial differences in individual components. There is evidence of remaining regional data-gaps. Estimates remain particularly poorly constrained for soils in the High Arctic region and physiographic regions with thin sedimentary overburden (mountains, highlands and plateaus) as well as for 〉3 m depth deposits in deltas and the Yedoma region.

Beschreibung: Identification of the pre-glacial, transitional and full glacial components in the deep-sea sedimentary record is necessary to understand the ice sheet development of Antarctica and to build circum-Antarctic sediment thickness grids for palaeotopography/-bathymetry reconstructions, which constrain palaeoclimate models. A ~3300 km long Weddell Sea to Scotia Sea multichannel seismic reflection data transect was constructed to define the first basin-wide seismostratigraphy and to identify the pre-glacial to glacial components. Seven main seismic units were mapped: Of these, WS-S1, WS-S2 and WS-S3 comprise the inferred Cretaceous– Palaeocene pre-glacial regime (〉27 Ma in our age model), WS-S4 the Eocene–Oligocene transitional regime (27–11 Ma) and WS-S5, WS-S6, WS-S7 the Miocene–Pleistocene full glacial climate regime (11–1 Ma). Sparse borehole data from ODP Leg 113 and SHALDRIL constrain the ages of the upper three seismic units and seafloor spreading magnetic anomalies compiled from literature constrain the basement ages in the presented age model. The new horizons and stratigraphy often contradict local studies and show an increase in age from southeast to the northwest. The up to 1130 m thick pre-glacial seismic units form a mound in the central Weddell Sea basin and in conjunction with the eroded flank geometry, allow the interpretation of a Cretaceous proto-Weddell Gyre bottom current. The base reflector of the transitional seismic unit has a model age of 26.6–15.5 Ma from southeast to northwest, suggesting similar southeast to northwest initial ice sheet propagation to the outer shelf. We interpret an Eocene East Antarctic Ice Sheet expansion, Oligocene grounding of the West Antarctic Ice Sheet and Early Miocene grounding of the Antarctic Peninsula Ice Sheet. The transitional regime sedimentation rates in the central and northwestern Weddell Sea (6–10 cm/ky) are higher than in the pre-glacial (1–3 cm/ky) and full glacial regimes (4–8 cm/ky). The pre-glacial to glacial rates are highest in the Jane- and Powell Basins (10–12 cm/ky). Total sediment volume in the Weddell Sea deep-sea basin is estimated at 3.3–3.9×10^6 km3.

Beschreibung: The trophic structure of the German Bight soft-bottom benthic community was evaluated for potential changes after cessation of bottom trawling. Species were collected with van-Veen grabs and beam trawls. Trophic position (i.e. nitrogen stable isotope ratios, δ15N) and energy flow (i.e. species metabolism approximated by body mass scaled abundance) of dominant species were compared in trawled areas and an area protected from fisheries for 14 months in order to detect trawling cessation effects by trophic characteristics. At the community level, energy flow was lower in the protected area, but we were unable to detect significant changes in trophic position. At the species level energy flow in the protected area was lower for predating/scavenging species but higher for interface feeders. Species trophic positions of small predators/scavengers were lower and of deposit feeders higher in the protected area. Major reasons for trophic changes after trawling cessation may be the absence of artificial and additional food sources from trawling likely to attract predators and scavengers, and the absence of physical sediment disturbance impacting settlement/survival of less mobile species and causing a gradual shift in food availability and quality. Our results provide evidence that species or community energy flow is a good indicator to detect trawling induced energy-flow alterations in the benthic system, and that in particular species trophic properties are suitable to capture subtle and short-term changes in the benthos following trawling cessation.

Beschreibung: High latitude terrestrial ecosystems are key components in the global carbon (C) cycle. The Northern Circumpolar Soil Carbon Database (NCSCD) was developed to quantify stocks of soil organic carbon (SOC) in the northern circumpolar permafrost region (18.7×106 km2 5 ). The NCSCD is a digital Geographical Information systems (GIS) database compiled from harmonized regional soil classification maps, in which data on soil coverage has been linked to pedon data from the northern permafrost regions. Previously, the NCSCD has been used to calculate SOC content (SOCC) and mass (SOCM) to the reference depths 0–30 cm and 0–100 cm (based on 1778 pedons). It 10 has been shown that soils of the northern circumpolar permafrost region also contain significant quantities of SOC in the 100–300 cm depth range, but there has been no circumpolar compilation of pedon data to quantify this SOC pool and there are no spatially distributed estimates of SOC storage below 100 cm depth in this region. Here we describe the synthesis of an updated pedon dataset for SOCC in deep soils 15 of the northern circumpolar permafrost regions, with separate datasets for the 100– 200 cm (524 pedons) and 200–300 cm (356 pedons) depth ranges. These pedons have been grouped into the American and Eurasian sectors and the mean SOCC for different soil taxa (subdivided into Histels, Turbels, Orthels, Histosols, and permafrost-free mineral soil taxa) has been added to the updated NCSCDv2. The updated version of 20 the database is freely available online in several different file formats and spatial resolutions that enable spatially explicit usage in e.g. GIS and/or terrestrial ecosystem models. The potential applications and limitations of the NCSCDv2 in spatial analyses are briefly discussed. An open access data-portal for all the described GIS-datasets is available online at: http://dev1.geo.su.se/bbcc/dev/v3/ncscd/download.php. The NC25 SCDv2 database has the doi:10.5879/ECDS/00000002.