English
norskBlar i forfatter "Martma, Tõnu"
Viser treff 1-7 av 7
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A 160,000-year-old history of tectonically controlled methane seepage in the Arctic
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-07)The geological factors controlling gas release from Arctic deep-water gas reservoirs through seabed methane seeps are poorly constrained. This is partly due to limited data on the precise chronology of past methane emission episodes. Here, we use uranium-thorium dating of seep carbonates sampled from the seabed and from cores drilled at the Vestnesa Ridge, off West Svalbard (79°N, ~1200 m water ... -
Discharge of Meteoric Water in the Eastern Norwegian Sea since the Last Glacial Period
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-03)Submarine groundwater discharge could impact the transport of critical solutes to the ocean. However, its driver(s), significance over geological time scales, and geographical coverage are poorly understood. We characterize a submarine groundwater seep from the continental slope off northern Norway where substantial amount of meteoric water was detected. We reconstruct the seepage history from ... -
Effect of glacial drainage water on the CO2 system and ocean acidification state in an Arctic tidewater-glacier fjord during two contrasting years
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-02-03)In order to investigate the effect of glacial water on the CO<sub>2</sub> system in the fjord, we studied the variability of the total alkalinity (A<sub>T</sub>), total dissolved inorganic carbon (C<sub>T</sub>), dissolved inorganic nutrients, oxygen isotopic ratio (δ<sup>18</sup>O), and freshwater fractions from the glacier front to the outer Tempelfjorden on Spitsbergen in winter 2012 (January, ... -
Influence of glacial water and carbonate minerals on wintertime sea-ice biogeochemistry and the CO2 system in an Arctic fjord in Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-13)The effect of freshwater sources on wintertime sea-ice CO2 processes was studied from the glacier front to the outer Tempelfjorden, Svalbard, in sea ice, glacier ice, brine and snow. March–April 2012 was mild, and the fjord was mainly covered with drift ice, in contrast to the observed thicker fast ice in the colder April 2013. This resulted in different physical and chemical properties of the sea ... -
Protracted post-glacial hydrocarbon seepage in the Barents Sea revealed by U–Th dating of seep carbonates
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-03-01)The hydrocarbon seepage chronology during deglaciation across the formerly glaciated Barents Sea was established using uranium-thorium (U–Th) dating of seep carbonates. Seep carbonates were sampled with remotely operated vehicles (ROV) from the seafloor at three active hydrocarbon seeps (water depth 156–383 m), located in the north-west (Storfjordrenna), north-central (Storbanken High), and south-west ... -
Timescales of methane seepage on the Norwegian margin following collapse of the Scandinavian Ice Sheet
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-05-11)Gas hydrates stored on continental shelves are susceptible to dissociation triggered by environmental changes. Knowledge of the timescales of gas hydrate dissociation and subsequent methane release are critical in understanding the impact of marine gas hydrates on the ocean–atmosphere system. Here we report a methane efflux chronology from five sites, at depths of 220–400 m, in the southwest Barents ... -
U-Th chronology and formation controls of methane-derived authigenic carbonates from the Hola trough seep area, northern Norway
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-10-20)We investigated methane-derived authigenic carbonate (MDAC) crusts and nodules from a cold seep site on the northern Norwegian continental shelf in ca. 220 m water depth to determine the timing and mode of their formation. Gas bubbling observed during remotely operated vehicle (ROV)-assisted sampling of MDAC crusts revealed ongoing seep activity. Authigenic carbonates were present as crusts on the ...
