Effects of sea ice cover on acoustic ray travel times, with applications to the Greenland Sea tomography experiment

Jin, Guoliang; Lynch, Jim; Pawlowicz, Rich; Wadhams, Peter

doi:10.1121/1.406951

Cited by 22 publications

(7 citation statements)

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“…(ii) The use of acoustic techniques. It has been shown that travel time changes for an acoustic path are reduced by the presence of an ice cover, in most cases by an amount approximately proportional to the ice thickness (Guoliang and Wadhams 1989;Jin et al 1993). In long-range acoustic propagation experiments this can be used to give a single mean value for ice thickness along a path.…”

Section: Future Measurement Needsmentioning

confidence: 98%

Arctic Ice Cover, Ice Thickness and Tipping Points

Wadhams

2012

AMBIO

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We summarize the latest results on the rapid changes that are occurring to Arctic sea ice thickness and extent, the reasons for them, and the methods being used to monitor the changing ice thickness. Arctic sea ice extent had been shrinking at a relatively modest rate of 3-4% per decade (annually averaged) but after 1996 this speeded up to 10% per decade and in summer 2007 there was a massive collapse of ice extent to a new record minimum of only 4.1 million km(2). Thickness has been falling at a more rapid rate (43% in the 25 years from the early 1970s to late 1990s) with a specially rapid loss of mass from pressure ridges. The summer 2007 event may have arisen from an interaction between the long-term retreat and more rapid thinning rates. We review thickness monitoring techniques that show the greatest promise on different spatial and temporal scales, and for different purposes. We show results from some recent work from submarines, and speculate that the trends towards retreat and thinning will inevitably lead to an eventual loss of all ice in summer, which can be described as a 'tipping point' in that the former situation, of an Arctic covered with mainly multi-year ice, cannot be retrieved.

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Section: Future Measurement Needsmentioning

confidence: 98%

Arctic Ice Cover, Ice Thickness and Tipping Points

Wadhams

2012

AMBIO

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“…Nominal accuracy for the latter system is no better than AE0.5m in thickness. 13 Other, more exotic, thickness estimation methods also have been proposed based upon horizontal acoustic ray travel times 14,15 and from anomalous peaks in the flexural wave spectrum of floating ice covers. 16 In both cases, simplifying assumptions about the character of the ice covers appear to be difficult to justify.…”

Section: Above Surface Approachesmentioning

confidence: 99%

Advances in upward looking sonar technology for studying the processes of change in Arctic Ocean ice climate

Fissel

Marko

Melling

2008

Journal of Operational Oceanography

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A major impetus for scientific studies of climate change in the Arctic Ocean has been the reduction in the areal extent and thickness of its sea ice cover. An extended measurement record of the horizontal dimensions of this ice cover is available for the full Arctic Ocean Basin based upon a record compiled from more than 30 years of relatively continuous satellite based measurements. Unfortunately, data accumulations for the ice cover's vertical dimension, ie, sea ice thickness, tend to be limited to data sets with durations no longer than 15 years, reflecting underlying greater measurement difficulties. Moreover, the longest duration ice thickness data collection efforts have been confined only to two specific portions of the Basin, namely, Fram Strait and the Canadian sector of the Beaufort Sea. Elsewhere, the available data sets are either of notably shorter duration or non-existent.Upward-looking sonar (ULS) has been and continues to be the primary source of data with volumes and accuracy sufficient for meaningfully monitoring ice thickness. Originally deployed from polar-traversing submarines during the Cold War, the limited amounts and accessibility of the collected data stimulated development of purpose-built sea-floor moored ULS instrumentation which, beginning in the late 1980s, began to supply the bulk of newly acquired ice draft and ice under-surface topography data. Technological advances have subsequently led to new generations of ULS instruments including ice-profiling sonar (IPS), incorporating much expanded on-board data storage capacities (69 Mbytes to 8 Gbytes) and powerful real-time firmware which now allow unprecedented temporal (ping rates of up to 1Hz) and horizontal resolution of ice topography. These instruments operate autonomously during one year or longer deployments, returning draft data on time and spatial scales of 1s and 1m or better, respectively, which are essential to understandings of mechanical and thermodynamical aspects of sea ice processes. Such processes govern ocean-atmosphere exchanges in polar waters, thereby determining ice extent and thickness parameters. The larger data storage

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“…Acoustic experimental researches in the Arctic region can be traced back to the last century [3]. The ice area, climate, and earthquakes were monitored through the experimental data of underwater acoustic propagation [4,5].…”

Section: Introductionmentioning

confidence: 99%

Reflection Characteristics of a Near‐Interface Cavity in Ice at Supercritical Incidence

Wang

Zhu

Yin

et al. 2019

Mathematical Problems in Engineering

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The long-range propagation modes in an acoustic channel under ice are basically caused by supercritical incidence. The energy distribution and transmission loss in the acoustic channel under ice are changed by a scatter in ice. The influence of a slender cylindrical cavity near and parallel to the ice-water interface on the sound propagation is analyzed using Fourier-Bessel series and Sommerfeld-Watson transformation. The research found that the acoustic field presents a beam in the mirror reflection direction at supercritical incidence, and the beam-width is proportional to secant of incident angle; meanwhile, the reflected coefficient is proportional to cosine of incident angle. The reflection coefficient increases with relative depth and Helmholtz number if the incident angle is a constant.

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Effects of sea ice cover on acoustic ray travel times, with applications to the Greenland Sea tomography experiment

Cited by 22 publications

References 0 publications

Arctic Ice Cover, Ice Thickness and Tipping Points

Arctic Ice Cover, Ice Thickness and Tipping Points

Advances in upward looking sonar technology for studying the processes of change in Arctic Ocean ice climate

Reflection Characteristics of a Near‐Interface Cavity in Ice at Supercritical Incidence

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