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The configuration, sensitivity and rapid retreat of the Late Weichselian Icelandic ice sheet
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-02-03)
The fragmentary glacial-geological record across the Icelandic continental shelf has hampered reconstruction of the volume, extent and chronology of the Late Weichselian ice sheet particularly in key offshore zones. Marine geophysical data collected over the last two decades reveal that the ice sheet likely attained a continental shelf-break position in all sectors during the Last Glacial Maximum, ...
Physical Conditions of Fast Glacier Flow: 2. Variable Extent of Anisotropic Ice and Soft Basal Sediment From Seismic Reflection Data Acquired on Store Glacier, West Greenland
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-01-09)
Outlet glaciers of the Greenland Ice Sheet transport ice from the interior to the ocean and contribute directly to sea level rise because discharge and ablation often exceed the accumulation. To develop a better understanding of these fast‐flowing glaciers, we investigate the basal conditions of Store Glacier, a large outlet glacier flowing into Uummannaq Fjord in west Greenland. We use two crossing ...
How robust are in situ observations for validating satellite-derived albedo over the dark zone of the Greenland Ice Sheet?
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-07-17)
Calibration and validation of satellite‐derived ice sheet albedo data require high‐quality, in situ measurements commonly acquired by up and down facing pyranometers mounted on automated weather stations (AWS). However, direct comparison between ground and satellite‐derived albedo can only be justified when the measured surface is homogeneous at the length‐scale of both satellite pixel and in situ ...
Supraglacial ponds regulate runoff from Himalayan debris-covered glaciers
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-29)
Meltwater and runoff from glaciers in High Mountain Asia is a vital freshwater resource for
one-fifth of the Earth’s population. Between 13% and 36% of the region’s glacierized areas exhibit surface
debris cover and associated supraglacial ponds whose hydrological buffering roles remain unconstrained.
We present a high-resolution meltwater hydrograph from the extensively debris-covered Khumbu ...
Dark zone of the Greenland Ice Sheet controlled by distributed biologically-active impurities
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-14)
Albedo—a primary control on surface melt—varies considerably across the Greenland Ice Sheet yet the specific surface types that comprise its dark zone remain unquantified. Here we use UAV imagery to attribute seven distinct surface types to observed albedo along a 25 km transect dissecting the western, ablating sector of the ice sheet. Our results demonstrate that distributed surface impurities—an ...
Holocene atmospheric circulation in the central North Pacific: A new terrestrial diatom and d18O dataset from the Aleutian Islands
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-02)
The North Pacific is a zone of cyclogenesis that modulates synoptic-scale atmospheric circulation, yet there is a paucity of instrumental and paleoclimate data to fully constrain its long-term state and variability. We present the first Holocene oxygen isotope record (δ<sup>18</sup>O<sub>diatom</sub>) from the Aleutian Islands, using siliceous diatoms preserved in Heart Lake on Adak Island (51.85° ...
Gas hydrate dissociation off Svalbard induced by isostatic rebound rather than global warming
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-01-08)
Methane seepage from the upper continental slopes of Western Svalbard has previously
been attributed to gas hydrate dissociation induced by anthropogenic warming of ambient
bottom waters. Here we show that sediment cores drilled off Prins Karls Foreland contain
freshwater from dissociating hydrates. However, our modeling indicates that the observed
pore water freshening began around 8 ka BP when ...
Deglaciation of the Eurasian ice sheet complex
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-14)
The Eurasian ice sheet complex (EISC) was the third largest ice mass during the Last Glacial Maximum with a span of over 4500 km and responsible for around 20 m of eustatic sea-level lowering. Whilst recent terrestrial and marine empirical insights have improved understanding of the chronology, pattern and rates of retreat of this vast ice sheet, a concerted attempt to model the deglaciation of the ...
Ice-sheet-driven methane storage and release in the Arctic
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-01-07)
It is established that late-twentieth and twenty-first century ocean warming has forced
dissociation of gas hydrates with concomitant seabed methane release. However, recent dating of
methane expulsion sites suggests that gas release has been ongoing over many millennia. Here we
synthesize observations of B1,900 fluid escape features—pockmarks and active gas flares—across a
previously glaciated ...
The build-up, configuration, and dynamical sensitivity of the Eurasian ice-sheet complex to Late Weichselian climatic and oceanic forcing
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-12-01)
The Eurasian ice-sheet complex (EISC) was the third largest ice mass during the Last Glacial Maximum (LGM), after the Antarctic and North American ice sheets. Despite its global significance, a comprehensive account of its evolution from independent nucleation centres to its maximum extent is conspicuously lacking. Here, a first-order, thermomechanical model, robustly constrained by empirical evidence, ...