• Glacially Induced Stress Across the Arctic From the Eemian Interglacial to the Present—Implications for Faulting and Methane Seepage 

      Vachon, Remi Elie Celestin; Schmidt, P.; Lund, Bjorn; Plaza-Faverola, Andreia; Patton, Henry; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06-28)
      Strong compressive and shear stresses generated by glacial loading and unloading have a direct impact on near-surface geological processes. Glacial stresses are constantly evolving, creating stress perturbations in the lithosphere that extend significant distances away from the ice. In the Arctic, periodic methane seepage and faulting have been recurrently associated with glacial cycles. However, ...
    • Glacier algae accelerate melt rates on the south-western Greenland Ice Sheet 

      Cook, Joseph M.; Tedstone, Andrew J.; Williamson, Christopher; McCutcheon, Jenine; Hodson, Andrew J.; Dayal, Archana; Skiles, McKenzie; Hofer, Stefan; Bryant, Robert; McAree, Owen; McGonigle, Andrew; Ryan, Jonathan; Anesio, Alexandre M.; Irvine-Fynn, Tristram D.L.; Hubbard, Alun Lloyd; Hanna, Edward; Flanner, Mark; Mayanna, Sathish; Benning, Liane G.; van As, Dirk; Yallop, Marian; McQuaid, James B.; Gribbin, Thomas; Tranter, Martyn (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-29)
      Melting of the Greenland Ice Sheet (GrIS) is the largest single contributor to eustatic sea level and is amplified by the growth of pigmented algae on the ice surface, which increases solar radiation absorption. This biological albedo-reducing effect and its impact upon sea level rise has not previously been quantified. Here, we combine field spectroscopy with a radiative-transfer model, supervised ...
    • Greenland ice sheet climate disequilibrium and committed sea-level rise 

      Box, Jason E.; Hubbard, Alun Lloyd; Bahr, David B.; Colgan, William T.; Fettweis, Xavier; Mankoff, Kenneth D.; Wehrlé, Adrien; Noel, Brice; Van Den Broeke, Michiel R.; Wouters, Bert; Bjørk, Anders A.; Fausto, Robert S. (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-29)
      Ice loss from the Greenland ice sheet is one of the largest sources of contemporary sea-level rise (SLR). While process-based models place timescales on Greenland’s deglaciation, their confidence is obscured by model shortcomings including imprecise atmospheric and oceanic couplings. Here, we present a complementary approach resolving ice sheet disequilibrium with climate constrained by satellite-derived ...
    • Holocene atmospheric circulation in the central North Pacific: A new terrestrial diatom and d18O dataset from the Aleutian Islands 

      Bailey, Hannah L.; Kaufman, Darrell S.; Sloane, Hilary J.; Hubbard, Alun Lloyd; Henderson, Andrew C.G.; Leng, Melanie J.; Meyer, Hanno; Welker, Jeffrey M. (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° ...
    • How robust are in situ observations for validating satellite-derived albedo over the dark zone of the Greenland Ice Sheet? 

      Ryan, J.C.; Hubbard, Alun Lloyd; Irvine-Fynn, T.; Doyle, S.H.; Cook, J.M.; Stibal, Marek; Box, J.E. (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 ...
    • Hydrocarbon leakage driven by quaternary glaciations in the Barents Sea based on 2D basin and petroleum system modeling 

      Kishankov, Aleksei; Serov, Pavel; Bünz, Stefan; Patton, Henry Jared; Hubbard, Alun Lloyd; Mattingsdal, Rune; Vadakkepuliyambatta, Sunil; Andreassen, Karin Marie (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-25)
      The Barents Sea has experienced intense erosion throughout the Cenozoic due to uplift and repeated episodes of glaciation. This, in turn, has driven large pressure and temperature fluctuations in the sediment substrate along with rearrangement of thermogenic oil and gas accumulations. As a result, some hydrocarbon fields have relatively shallow depths, and natural gas release is widespread. This ...
    • Ice-sheet-driven methane storage and release in the Arctic 

      Portnov, Aleksei D; Vadakkepuliyambatta, Sunil; Mienert, Jurgen; Hubbard, Alun Lloyd (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 ...
    • Icelandic permafrost dynamics since the Last Glacial Maximum – model results and geomorphological implications 

      Etzelmüller, Bernd; Patton, Henry; Schomacker, Anders; Czekirda, Justyna; Girod, Luc; Hubbard, Alun Lloyd; Lilleøren, Karianne Staalesen; Westermann, Sebastian (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-14)
      Iceland’s periglacial realm is one of the most dynamic on the planet, with active geomorphologicalprocesses and high weathering rates of young bedrock resulting in high sediment yields and ongoingmass movement. Permafrost is discontinuous in Iceland’s highlands and mountains over c. 800 m a.s.l,and sporadic in palsa mires in the central highlands. During the late Pleistocene and Holocene, ...
    • Methods for Predicting the Likelihood of Safe Fieldwork Conditions in Harsh Environments 

      Leidman, Sasha Z.; Rennermalm, Åsa K.; Broccoli, Anthony J.; van As, Dirk; van den Broeke, Michiel R.; Steffen, Konrad; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-07-30)
      Every year, numerous field teams travel to remote field locations on the Greenland ice sheet to carry out polar research, geologic exploration, and other commercial, military, strategic, and recreational activities. In this region, extreme weather can lead to decreased productivity, equipment failure, increased stress, unexpected logistical challenges, and, in the worst cases, a risk of physical ...
    • Microseismicity linked to gas migration and leakage on the western Svalbard shelf 

      Franek, Peter; Plaza-Faverola, Andreia; Mienert, Jurgen; Bünz, Stefan; Ferré, Benedicte; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-26)
      The continental margin off Prins Karls Forland, western Svalbard, is characterized by widespread natural gas seepage into the water column at and upslope of the gas hydrate stability zone. We deployed an ocean bottom seismometer integrated into the MASOX (Monitoring Arctic Seafloor-Ocean Exchange) automated seabed observatory at the pinch-out of this zone at 389 m water depth to investigate passive ...
    • Modification of bedrock surfaces by glacial abrasion and quarrying: Evidence from North Wales 

      Glasser, Neil F.; Roman, Matej; Holt, Tom O.; Žebre, Manja; Patton, Henry; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-30)
      Abrasion and quarrying are significant processes of subglacial erosion for ice masses in direct contact with hard substrates, yet their relative efficacy and spatio-temporal variability is unclear. Here, we investigate the glacial impact of these processes on a 70 m by 60 m bedrock surface at Moel Ysgyfarnogod in the Rhinog Mountains, Wales, using a combination of high-resolution digital photographs, ...
    • 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 

      Hofstede, C.; Christoffersen, P.; Hubbard, B.; Doyle, S.H.; Young, T.J.; Diez, A.; Eisen, O.; Hubbard, Alun Lloyd (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 ...
    • Physical Conditions of Fast Glacier Flow: 3.Seasonally-Evolving Ice Deformation onStore Glacier, West Greenland 

      Young, Tun Jan; Christoffersen, Poul; Doyle, Samuel H.; Nicholls, Keith W.; Stewart, C.L.; Hubbard, Bryn; Hubbard, Alun Lloyd; Lok, Lai B.; Brennan, Paul V.; Benn, Douglas I; Luckman, Adrian; Bougamont, Marion H. (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-01-08)
      Temporal variations in ice sheet flow directly impact the internal structure within ice sheetsthrough englacial deformation. Large-scale changes in the vertical stratigraphy within ice sheets havebeen previously conducted on centennial to millennial timescales; however, intra-annual changes inthe morphology of internal layers have yet to be explored. Over a period of 2 years, we use autonomousphas ...
    • Postglacial response of Arctic Ocean gas hydrates to climatic amelioration 

      Serov, Pavel; Vadakkepuliyambatta, Sunil; Mienert, Jurgen; Patton, Henry; Portnov, Aleksei D; Silyakova, Anna; Panieri, Giuliana; Carroll, Michael Leslie; Carroll, JoLynn; Andreassen, Karin; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-05)
      Seafloor methane release due to the thermal dissociation of gas hydrates is pervasive across the continental margins of the Arctic Ocean. Furthermore, there is increasing awareness that shallow hydrate-related methane seeps have appeared due to enhanced warming of Arctic Ocean bottom water during the last century. Although it has been argued that a gas hydrate gun could trigger abrupt climate ...
    • Rapid development and persistence of efficient subglacial drainage under 900 m-thick ice in Greenland 

      Chandler, David Matthew; Wadham, Jemma Louise; Nienow, Peter W.; Doyle, Samuel H.; Tedstone, Andrew J.; Telling, Jon; Hawkings, Jonathan R.; Alcock, Jonathan; Linhoff, Benjamin; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-11)
      Intensive study of the Greenland Ice Sheet's (GrIS) subglacial drainage has been motivated by its importance for ice dynamics and for nutrient/sediment export to coastal ecosystems. This has revealed consistent seasonal development of efficient subglacial drainage in the lower ablation area. While some hydrological models show qualitative agreement with field data, conflicting evidence (both field- ...
    • Resolving the internal and basal geometry of ice masses using imaging phase-sensitive radar 

      Young, Tun Jan; Schroeder, Dustin M.; Christoffersen, Poul; Lok, Lai B.; Nicholls, Keith W.; Brennan, Paul V.; Doyle, Samuel H.; Hubbard, Bryn; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-19)
      The phase-sensitive radio-echo sounder (pRES) is a powerful new instrument that can measure the depth of internal layers and the glacier bed to millimetre accuracy. We use a stationary 16-antenna pRES array on Store Glacier in West Greenland to measure the three-dimensional orientation of dipping internal reflectors, extending the capabilities of pRES beyond conventional depth sounding. This novel ...
    • Rock glaciers in central Patagonia 

      Selley, Heather; Harrison, Stephan; Glasser, Neil; Wündrich, Olaf; Colson, Daniel; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-10-22)
      Active rock glaciers are ice and debris-cored landforms common in cold arid mountains. They have not been widely described in the Patagonian Andes of southern South America and here we provide the first rock glacier inventory for the Jeinimeni region to the east of the contemporary North Patagonian Icefield. Detailed analysis of available satellite imagery and fieldwork demonstrates the presence of ...
    • The role of ocean and atmospheric dynamics in the marine-based collapse of the last Eurasian Ice Sheet 

      Sejrup, Hans Petter; Hjelstuen, Berit Oline Blihovde; Patton, Henry; Esteves, Mariana; Winsborrow, Monica; Rasmussen, Tine Lander; Andreassen, Karin Marie; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-05-19)
      Information from former ice sheets may provide important context for understanding the response of today’s ice sheets to forcing mechanisms. Here we present a reconstruction of the last deglaciation of marine sectors of the Eurasian Ice Sheet, emphasising how the retreat of the Norwegian Channel and the Barents Sea ice streams led to separation of the British-Irish and Fennoscandian ice sheets at ...
    • Seismic evidence for complex sedimentary control of Greenland Ice Sheet flow 

      Kulessa, Bernd; Hubbard, Alun Lloyd; Booth, Adam D.; Bougamont, Marion; Dow, Christine F.; Doyle, Samuel H.; Christoffersen, Poul; Lindbäck, Katrin; Pettersson, Rickard; Fitzpatrick, Andrew A.W.; Jones, Glenn A. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-08-16)
      The land-terminating margin of the Greenland Ice Sheet has slowed down in recent decades, although the causes and implications for future ice flow are unclear. Explained originally by a self-regulating mechanism where basal slip reduces as drainage evolves from low to high efficiency, recent numerical modeling invokes a sedimentary control of ice sheet flow as an alternative hypothesis. Although ...
    • Storage and export of microbial biomass across the western Greenland Ice Sheet 

      Irvine-Fynn, Tristram D.L.; Edwards, A.; Stevens, I.T.; Mitchell, A.C.; Bunting, P.; Box, J.E.; Cameron, K.A.; Cook, J.M.; Naegeli, K.; Rassner, S.M.E.; Ryan, J.C.; Stibal, M.; Williamson, C.J.; Hubbard, Alun Lloyd (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-25)
      The Greenland Ice Sheet harbours a wealth of microbial life, yet the total biomass stored or exported from its surface to downstream environments is unconstrained. Here, we quantify microbial abundance and cellular biomass flux within the near-surface weathering crust photic zone of the western sector of the ice sheet. Using groundwater techniques, we demonstrate that interstitial water flow is slow ...