An Analysis Of Ice Profiles Obtained By Submarine Sonar In The Beaufort Sea

Wadhams, Peter; Horne, R. J.

doi:10.1017/s0022143000015264

Cited by 126 publications

(47 citation statements)

References 12 publications

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“…Temporal parameters 2.3.1. Ice ridge identification criterion Ridges were identified using the Rayleigh criterion with a threshold value of 2.5 m and a minimum draft of 5 m Wadhams and Horne (1980). This choice was done to be in line with previous work such as those of Melling and Riedel (1996), Wadhams and Davis (2000), and Wadhams et al (2011).…”

Section: Ridge Keel Geometrymentioning

confidence: 99%

Ice ridge keel geometry and shape derived from one year of upward looking sonar data in the Fram Strait

Ekeberg

Høyland

Hansen

2015

Cold Regions Science and Technology

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Ice ridge keel geometry was studied by analyzing one year of upward looking sonar data collected in the Transpolar drift stream at 79°N, 6.5°W in 2008/2009. Ridges were identified using the Rayleigh criterion with a threshold value of 2.5 m and a minimum draft of 5 m. The keel shape was studied after the identification of ridges from temporal data. On average ridge keels were symmetric both with respect to the centroid of the keel and the keel crest location. By quantifying the ratio between observed keel area and the keel area of an assumed triangular keel shape (often assumed for first year ridges) we observed that in 79% of the cases the ridge cross sectional area would be underestimated by a triangular keel shape. Because keel loads on ships and structures increase with keel draft and keel area it is important that an assumed keel shape maintains the observed keel area. Thus we suggest that a better generalization of the shape of first year ridges is a trapezoidal keel shape rather than triangular. Based on the observations the mean trapezoidal keel, representing both first year ridges and old ridges, has a keel bottom-width which on average is 17% of the keel width. For the deepest keels (N 15 m) the mean keel bottom width was 12% of the keel width. The mean keel draft was 7.3 m and the deepest ridge was 25 m. The temporal data was converted to spatial data based on an ice drift speed estimate which assumed free drift. From the spatial data we found that the mean keel width was 28 m and the mean keel cross sectional area was 164 m 2 .

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Section: Ridge Keel Geometrymentioning

confidence: 99%

Ice ridge keel geometry and shape derived from one year of upward looking sonar data in the Fram Strait

Ekeberg

Høyland

Hansen

2015

Cold Regions Science and Technology

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“…Narrow leads, tens to hundreds of meters wide, and often hundreds of kilometers long, are the predominant site of open water and young ice within the winter Arctic ice pack. Rapid thermodynamic growth of thinner ice maintains a low fraction of open water cover throughout the winter [ Wadhams and Horne , 1980]. Maykut [1978] states that leads represent about 1% of the sea ice pack.…”

Section: Detecting Sea Surface Elevations and Measuring Freeboardmentioning

confidence: 99%

Five years of Arctic sea ice freeboard measurements from the Ice, Cloud and land Elevation Satellite

Farrell¹,

Laxon

McAdoo³

et al. 2009

J. Geophys. Res.

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[1] Using data from the first Earth-orbiting laser altimeter, the Geoscience Laser Altimeter System (GLAS), onboard the Ice, Cloud and land Elevation Satellite (ICESat), we analyze sea ice freeboard in the Arctic Ocean. We describe a new method for sea surface height retrieval, which relies on an algorithm that discriminates laser pulse reflections originating over leads or thin ice. The lead detection algorithm is based on surface reflectivity and analysis of parameters associated with the shape of reflected waveforms. Using knowledge of the local sea surface height and sea ice elevation, we estimate sea ice freeboard and present, for the first time, a time series of Arctic freeboard spanning 5 years between March 2003 and 2008. While the autumn (October-November) and winter (February-March) data illustrate the seasonal and interannual variations in freeboard, following the September 2007 record minimum sea ice extent, the autumn 2007 and winter 2008 spatially averaged freeboards are below the seasonal means at À4.5 cm and À6.8 cm, respectively. Over the observation period, mean freeboard has declined at a rate of $À1.8 cm/a during the autumn period and $À1.6 cm/a during the winter period, in the region bounded by the northern limit of ICESat coverage at 86°N. Because of the short 5-year observation period, it is unclear whether these results represent a long-term, downward trend in Arctic freeboard or are part of a natural variability. Furthermore, since the variability of snow thickness is included in the ICESat freeboard signal, a decrease in the freeboard cannot wholly be attributed to a decrease in sea ice thickness.

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“…On the basis of the observations of Ruffieux et al (1995) and Pinto et al (2003), one can estimate that a large lead (width of about 500 m) opening up directly upwind of an ice station can cause an increase of roughly 0.5 to 2 K in T 2 m (the exact value depending on several factors). Further, the opening up of a lead as wide as 500 m just upwind of an ice station in the central Arctic is a rare event [see Wadhams and Horne (1981) for lead statistics].…”

Section: Introductionmentioning

confidence: 99%

On the Factors Controlling the Snow Surface and 2-m Air Temperatures Over the Arctic Sea Ice in Winter

Vihma¹,

Pirazzini

2005

Boundary-Layer Meteorol

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Factors controlling the magnitudes of, and short-term variations in, the potential temperatures of the snow surface and the air at the height of 2 m (h S and h 2 m ) over Arctic sea ice in winter are analysed. The study addresses the winters of 1986-1987 and 1987-1988, and is based on the temperature, wind, and cloud observations made by Russian drifting ice stations. It also relies on the ERA40 re-analyses of the European Centre for Medium-Range Weather Forecasts, which were utilised to calculate the lateral heat advection at the sites of the ice stations. The cloud cover and wind speed were more important than the heat advection in controlling the magnitudes of h 2 m and h S , while on a time scale of 24 h, during steady forcing conditions, the heat advection was the most important factor affecting the changes in h S and h 2 m . During changing conditions, and considering individual factors separately, the monthly mean 24-h temperature changes were less than ± 5°C: the effect of the cloud cover was the largest, and that of the heat advection was the smallest. When simultaneous changes in the three factors were analysed, the seasonal mean temperature changes were even of the order of ±15°C, with the strongest warming events exceeding 35 K in a single day. The difference h S ) h 2 m reached its lowest seasonal mean values during conditions of clear skies ()1.3°C), light winds ()1.3°C) and warm-air advection ()0.8°C). h S and h 2 m followed each other closely, even during major synoptic-scale temperature variations.

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An Analysis Of Ice Profiles Obtained By Submarine Sonar In The Beaufort Sea

Cited by 126 publications

References 12 publications

Ice ridge keel geometry and shape derived from one year of upward looking sonar data in the Fram Strait

Ice ridge keel geometry and shape derived from one year of upward looking sonar data in the Fram Strait

Five years of Arctic sea ice freeboard measurements from the Ice, Cloud and land Elevation Satellite

On the Factors Controlling the Snow Surface and 2-m Air Temperatures Over the Arctic Sea Ice in Winter

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