Blar i forfatter "Howell, Stephen"

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    • A 10-year record of Arctic summer sea ice freeboard from CryoSat-2 

      Dawson, Geoffrey; Landy, Jack Christopher; Tsamados, Michel; Komarov, Alexander S.; Howell, Stephen; Heorten, Harold; Krumpen, Thomas (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-29)
      Satellite observations of pan-Arctic sea ice thickness have so far been constrained to winter months. For radar altimeters, conventional methods cannot differentiate leads from meltwater ponds that accumulate at the ice surface in summer months, which is a critical step in the ice thickness calculation. Here, we use over 350 optical and synthetic aperture radar (SAR) images from the summer months ...

    • High spatial and temporal resolution L- and C-band Synthetic Aperture Radar data analysis from the yearlong MOSAiC expedition 

      Johansson, Malin; Singha, Suman; Spreen, Gunnar; Howell, Stephen; Sobue, Shin-ichi; Davidson, Malcolm (Conference object; Konferansebidrag, 2021-04)
      In the yearlong MOSAIC expedition (2019-2020) R/V Polarstern drifted with sea ice through the Arctic Ocean, with the goal to continually monitor changes in the coupled ocean-ice-atmosphere system throughout the seasons. A substantial amount of synthetic aperture radar (SAR) satellite images overlapping the campaign was collected. Here, we investigate the change in polarimetric features over sea ice ...

    • Increasing Multiyear Sea Ice Loss in the Beaufort Sea: A New Export Pathway for the Diminishing Multiyear Ice Cover of the Arctic Ocean 

      Babb, David G; Galley, Ryan; Howell, Stephen; Landy, Jack Christopher; Barber, David G. (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-05-16)
      Historically, multiyear sea ice (MYI) covered a majority of the Arctic and circulated through the Beaufort Gyre for years. However, increased ice melt in the Beaufort Sea during the early 2000s was proposed to have severed this circulation. Constructing a regional MYI budget from 1997 to 2021 reveals that MYI import into the Beaufort Sea has increased year-round, yet less MYI now survives through ...

    • Multi-Year Sea Ice Conditions in the Northwest Passage: 1968–2020 

      Howell, Stephen; Babb, David G; Landy, Jack Christopher; Brady, Michael (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-21)
      The Northwest Passage is often referred to as the “Holy Grail” of ship navigation as it provides a shorter route connecting the Atlantic and Pacific Oceans compared to the Northern Sea Route, Panama Canal, Suez Canal, and transiting around Cape Horn. Here, we summarize 52 years of observed multi-year ice (MYI) conditions from 1968 to 2020 in the western Canadian Arctic regions of the Northwest ...

    • Year-around C- and L-band observation around the MOSAiC ice floe with high spatial and temporal resolution 

      Singha, Suman; Johansson, Malin; Spreen, Gunnar; Howell, Stephen; Shin-ichi, Sobue; Davidson, Malcolm (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-12)
      In September 2019, the German research icebreaker Polarstern started the largest multidisciplinary Arctic expedition, the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) drift experiment. Being moored to ice floes at high Arctic for a whole year, thus including the winter season, the main goal of the expedition is to better understand and quantify relevant processes ...

    • A year-round satellite sea-ice thickness record from CryoSat-2 

      Landy, Jack Christopher; Dawson, Geoffrey; Tsamados, Michel; Bushuk, Mitchell; Stroeve, Julienne C.; Howell, Stephen; Krumpen, Thomas; Babb, David G.; Komarov, Alexander S.; Heorton, Harold; Belter, H. Jakob; Aksenov, Yevgeny (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-09-14)
      Arctic sea ice is diminishing with climate warming at a rate unmatched for at least 1,000 years. As the receding ice pack raises commercial interest in the Arctic, it has become more variable and mobile, which increases safety risks to maritime users. Satellite observations of sea-ice thickness are currently unavailable during the crucial melt period from May to September, when they would be most ...