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From the afternoon of April 1st to the morning of April 9th 2015, CAGE at the Department of Geology Uit, the Arctic University of Norway, arranged a scientific cruise aimed at investigating the western Barents Sea slope, western and northern Svalbard margin, methane seep sites at Vestnesa and Storfjorden Trough and the Barents Sea on R/V “Helmer Hanssen”. Investigated areas were (in order of visiting sites on the cruise): Malangen Trough, Bjørnøya Trough Mouth Fan south and mid, Storfjorden Fan, Vestnesa Ridge, the northwest Svalbard slope to north of Schmeerenburgfjorden. On the track towards Tromsø we sampled in Storfjorden Trough. The scientific sampling was done within the framework of several ongoing projects at the Department of Geology, University of Tromsø: “CAGE -Centre for Arctic Gas hydrate, Environment and Climate”, in which the sub-projects “Paleo-CIRCUS”, “OA-Ocean Acidification” is included. A total of 2 gravity cores, 8 plankton net casts and 22 CTD (conductivity-temperature-depth) casts were performed along the route to Northern Svalbard at the western Barents Sea slope. Data were also collected in Storfjorden Trough and the mouth of Storfjorden. In addition, CTD’s and a small chirp and multibeam survey was performed off Schmeerenburgfjorden, north of fjorden and in its northernmost part. Chirp profiles and multibeam lines were acquired during transits and during the survey of outer Schmeerenburgfjorden. The recording started from c. 71 N on the western Barents Sea slope and ended at 70.00 N. The cruise may be known as: CAGE15_1_CO2

The flow of the Atlantic Water (AW) via the Return Atlantic Current (RAC) regulates the oceanographical conditions in the Northwestern (NW) Greenland Sea in the Fram Strait. As the intensity of the RAC might significantly influence both deep-water formation in the area and the stability of the Northeast Greenland Ice Sheet (NE GIS), knowledge of its variability in the past is important. Here we present a reconstruction of the paleoceanographic forcing of the AW on climatic conditions and associated environmental changes in the NW Greenland Sea by means of foraminiferal assemblages, stable (oxygen and carbon) isotopes, and various sedimentological parameters from sediment core GR02-GC retrieved from NE Greenland continental slope (1170 m water depth). Our data indicate an almost continuous presence of AW in the NW Greenland Sea during the last 35 kyr BP. Two peaks of low planktic δ18O values at ~34.5 and 33 kyr BP are interpreted as meltwater signals associated with warm AW-induced melting of the adjacent NE GIS. The NE GIS advanced between 32 and 29 kyr BP, resulting in reduced meltwater influx to the NW Greenland Sea. Increased iceberg calving and melting after 29 kyr BP, were probably linked to surface warming and glacier advance to the shelf-break lasting until 23.5 kyr BP. During the Last Glacial Maximum, the extensive sea ice cover was associated with the presence of subsurface AW at the study site. During the Bølling–Allerød (B/A, ~14.6–12.7 kyr BP) strong melting of glaciers and sea ice was probably caused by the combined effect of the B/A warming and the flow of warm AW. The RAC was weakened during the Younger Dryas (~12.8–11.7 kyr BP), which reduced the advection of warm AW to the NW Greenland Sea. After 11.7 kyr BP, the RAC reached its modern strength, whereas, during the Holocene Thermal Maximum, it reached its maximum strength for the study period. In addition, short-term weakening of AW inflow to the core site was observed, especially at 10.5, 8.5, and 5.8 kyr BP.

One of four marine cores of glacial sediments collected from a water depth of about 1200 m at Vestnesa Ridge (west of Svalbard) contained small fragments of coal, charcoal and moss. This material was restricted to a single level, and 14C dating of bivalves both above and below indicates an age of c. 18.0–15.5 kyr BP. Chemical analyses of the coal indicate that the provenance area was from the northern part of Andøya, North Norway. The moss fragment was identified as Aulacomnium turgidum, which is a well-known species from the northern part of Andøya, which was an ice-free refugium with tundra vegetation during the Weichselian maximum. One small piece of charcoal with reasonably well-preserved cell structures is derived from burnt Salix sp. These findings are important, because they demonstrate the presence of drift ice carrying organic material from the northern part of Andøya towards the west coast of Svalbard during Heinrich event H1, an event of extensive ice-rafting in the Nordic seas. This also implies that some components of the vascular plant communities growing on Svalbard today, might originally have been imported as seeds floating on sea ice, before stranding along the coast of Svalbard. The plant colonization of Svalbard can thus have started already during Heinrich event H1. The finding of charcoal can only be explained by a fire due to lightning and not by campfire, because the first human population arrived in northern Norway at a much later time (probably during Preboreal). The charcoal is thus from the oldest known wild fire in Norway.

Four cores from Vestnesa Ridge on the western Svalbard margin from water depth of 1200 m have been studied. The Vestnesa Ridge is known for the presence of numerous pockmarks and active methane gas seepage is often observed in the form of acoustic gas flares. Three of the cores were collected from a pockmark with active seepage of methane and one core was taken just outside the seepage area for comparison. The cores show a range of influence from methane from no seepage (control core), moderate seepage, strong seepage to very strong seepage. All cores have been analyzed for the distribution of macrofossils, trace fossils, planktic foraminifera, stable isotopes, geochemistry and sedimentology. The main purpose of the study is to improve knowledge about the fossil macrofauna and past methane emissions in the area. The results show a major difference between the fauna recovered from cores taken inside a pockmark with chemosymbiotic bivalves and in some cases with a rich macrofauna and from the core recovered outside the pockmark that contained no macrofauna. The faunal relationships with the sedimentary environments confirm a close connection between the macrofauna and the presence/absence of cold-seepage, particularly seen in the occurrence of chemosymbiotic bivalves Archivesica arctica, Isorropodon nyeggaensis, potentially chemosymbiotic Rhacothyas kolgae and polychaetes. A barren zone in the core that was taken from the deepest part of the pockmark may indicate that a blow-out took place in the late glacial and the deglaciation into the early Holocene at c. 21,000–9000 years.