ORIGINAL Fluid flow and methane occurrences in the Disko Bugt area offshore West Greenland: indications for gas hydrates? Tove Nielsen & Troels Laier & Antoon Kuijpers & Tine L. Rasmussen & Naja E. Mikkelsen & Niels Nørgård-Pedersen Received: 19 December 2013 /Accepted: 28 August 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract The present study is the first to directly address the issue of gas hydrates offshore West Greenland, where numer- ous occurrences of shallow hydrocarbons have been docu- mented in the vicinity of Disko Bugt (Bay). Furthermore, decomposing gas hydrate has been implied to explain seabed features in this climate-sensitive area. The study is based on archive data and new (2011, 2012) shallow seismic and sed- iment core data. Archive seismic records crossing an elongat- ed depression (20×35 km large, 575 m deep) on the inner shelf west of Disko Bugt (Bay) show a bottom simulating reflector (BSR) within faulted Mesozoic strata, consistent with the occurrence of gas hydrates. Moreover, the more recently acquired shallow seismic data reveal gas/fluid-related features in the overlying sediments, and geochemical data point to methane migration from a deeper-lying petroleum system. By contrast, hydrocarbon signatures within faulted Mesozoic strata below the strait known as the Vaigat can be inferred on archive seismics, but no BSR was visible. New seismic data provide evidence of various gas/fluid-releasing features in the overlying sediments. Flares were detected by the echo- sounder in July 2012, and cores contained ikaite and showed gas-releasing cracks and bubbles, all pointing to ongoing methane seepage in the strait. Observed seabed mounds also sustain gas seepages. For areas where crystalline bedrock is covered only by Pleistocene–Holocene deposits, methane was found only in the Egedesminde Dyb (Trough). There was a strong increase in methane concentration with depth, but no free gas. This is likely due to the formation of gas hydrate and the limited thickness of the sediment infill. Seabed depres- sions off Ilulissat Isfjord (Icefjord) previously inferred to express ongoing gas release from decomposing gas hydrate show no evidence of gas seepage, and are more likely a result of neo-tectonism. Introduction Modelling of gas hydrate generation based on varying phys- iographic and oceanographic settings indicates that large parts of the continental margins surrounding Greenland could con- tain hydrates (e.g. Wallmann et al. 2012). In addition, a study addressing as yet undiscovered hydrocarbon resources north of the Arctic Circle suggests that offshore Mesozoic sedimen- tary basins on the West and Northeast Greenland margins could hold high quantities of oil and gas (Gautier et al. 2011). Due to late Cainozoic uplift and glacial erosion (Japsen et al. 2006), these basins are now exposed at the seabed or found at shallow sub-seabed depth (Hamann et al. 2005; Gregersen and Bidstrup 2008), increasing the probability for seepages of gas and thus for formation of gas hydrates. Presence of potential reservoirs of methane in the form of gas hydrates is significant for future petroleum exploration offshore Greenland. Gas hydrates are also a potential factor in global climate change. Dissociation of the hydrates may lead to increased acidification of the oceans and may release meth- ane to the atmosphere (e.g. Valentine et al. 2001; Biastoch et al. 2011; Smith et al. 2014). In the past decades the Arctic has experienced rapid warming, which according to present climate predictions may even accelerate in concert with the general decrease of the Arctic Ocean sea ice (Screen and Simmonds 2010). A long-term warming trend started, how- ever, already at the last glacial maximum (LGM), at which time the rising sea level and retreat of grounded ice sheets T. Nielsen (*) : T. Laier : A. Kuijpers : N. E. Mikkelsen : N. Nørgård-Pedersen Geological Survey of Denmark and Greenland, Øster Voldgade 10, 1350 Copenhagen, Denmark e-mail: tni@geus.dk T. L. Rasmussen CAGE – Centre for Arctic Gas Hydrate, Environment and Climate, UiT, Arctic University of Norway, Tromsø, Norway Geo-Mar Lett DOI 10.1007/s00367-014-0382-2