The under‐ice thickness distribution of the Arctic Basin as recorded in 1958 and 1970

Abstract

The USS Nautilus (SSN‐571) was the first vessel to cross the Arctic Basin via the north pole in early August 1958. During this expedition, almost continuous acoustic under‐ice thickness profiles were recorded. In August 1970 USS Queenfish (SSN‐651) retraced Nautilus' route, yielding the only duplicate transect of under‐ice topography across the Arctic Basin. Comparisons of the statistical analysis of the under‐ice draft measurements obtained through use of wide‐beam and narrow‐beam and narrow‐beam only acoustic profilers by Nautilus and Queenfish, respectively, along the coincidental route are presented. Geographic areas found to have distinct under‐ice characteristics and ice composition are identified. The under‐ice statistics of both cruises are considered in relation to representative field observations and modeling results of other researchers. Principal findings are (1) Nautilus recorded generally more severe ice conditions within the Canada Basin than did Queenfish 12 years later; overall mean drafts were 3.08 and 2.39 m, respectively, (2) the under‐ice topography becomes progressively more severe when proceeding from the Canadian to the Eurasian side of the Arctic Basin, (3) the Canada Basin may contain the most moderate under‐ice topography and the greatest number of open water and refrozen polynyas and leads within the central Arctic Basin, (4) the Makarov and Amundsen basins and the Arctic mid‐ocean ridge may contain some of the most severe under‐ice topography within the Arctic Basin, and (5) the present study indicates an overall Arctic Basin mean of 3–4% open water/new ice (less than 30 cm) in summer.

Sea‐ice draft from submarine‐based sonar: Establishing a consistent record from analog and digitally recorded data

“…The digitally recorded data, also referred to as DIPS data (for Digital Ice Profiling System), are referred to hereinafter as the digital data. Ice draft data have been used to examine topics such as quantifying the abundance of ice features (ridges and leads), assessing the spatial pattern of the Arctic ice cover [ Hibler , 1979; Bourke and Garrett , 1987], testing for climate change signals [ McLaren , 1989; McLaren et al , 1994; Shy and Walsh , 1996; Rothrock et al , 1999; Wadhams and Davis , 2000; Tucker et al , 2001] and testing sea ice models [ Zhang et al , 2003; Rothrock et al , 2003]. Some investigations have used only analog or only digital data; others have used mixtures of analog and digital data.…”

Surface characteristics and atmospheric footprint of springtime Arctic leads at SHEBA

“…The TIBL which formed over this lead influenced a large region downwind because of high wind speeds, a good fetch across the lead, limited ice growth and weak atmospheric stability. This lead was wider than most leads observed in the Arctic ice pack [ Mclaren , 1989], being wider than roughly 98% of all leads occurring in the Arctic. Solar heating during daylight hours reduced the near‐surface stability upwind of the lead which allowed for a deeper more vigorous plume capable of affecting a much broader region than that possible under stronger static stability.…”

“…The lead would have frozen over more rapidly if it had opened during off‐peak solar hours. Since this lead is larger than 98% of the leads typically observed in the Arctic Basin [ McLaren , 1989] and because it was observed during peak solar heating, it can be assumed all but the widest leads freeze over in less than 6 hours through mid‐spring despite solar heating. However, the length of time that a lead influences the atmosphere depends on the thickness of new ice in the lead as well.…”

Media and the Politics of Arctic Climate Change

“…Moreover, the routes of the submarines did not coincide, with few exceptions, making comparisons over time difficult but not impossible. Several studies discussed the thickness of the sea ice based on unclassified data from upward sonar measurements (LeSchack et al, 1971;Swithinbank, 1972;McLaren, 1989). In 1998, however, data that was also classified was released and was updated in 2006 and subsequently available for research (NSIDC, 1998).…”