To add to the growing information about the effect of multibeam echosounder (MBES) operation on marine mammals, a study was conducted to assess the spatial foraging effort of Cuvier’s beaked whales during two MBES surveys conducted in... more
To add to the growing information about the effect of multibeam echosounder (MBES) operation on marine mammals, a study was conducted to assess the spatial foraging effort of Cuvier’s beaked whales during two MBES surveys conducted in January of 2017 and 2019 off of San Clemente Island, California. The MBES surveys took place on the Southern California Antisubmarine Warfare Range (SOAR), which contains an array of 89 hydrophones covering an area of approximately 1800 km2over which foraging beaked whales were detected. A spatial autocorrelation analysis of foraging effort was conducted using the Moran’s I (global) and the Getis-Ord Gi∗(local) statistics, to understand the animals’ spatial use of the entire SOAR, as well as smaller areas, respectively, within the SOARBefore, During, andAfterthe two MBES surveys. In both years, the global Moran’s I statistic suggested significant spatial clustering of foraging events on the SOAR during all analysis periods (Before, During, andAfter). I...
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Quantitative analyses of multibeam sonar backscatter data have become increasingly important for a range of applications. A critical requirement for these applications is the ability to analyze the spatial and temporal variations of the... more
Quantitative analyses of multibeam sonar backscatter data have become increasingly important for a range of applications. A critical requirement for these applications is the ability to analyze the spatial and temporal variations of the backscatter data within a single survey or among several different surveys. In this paper, two backscatter surveys in Portsmouth Harbor, NH are used to evaluate different comparison techniques and infer the data requirements for comparison. The backscatter surveys were conducted in June 2007 by University of New Hampshire (UNH) and in September 2007 by Kongsberg in support of this conference. Both data sets were collected using an EM 3002D (300 kHz) installed on UNH’s R/V Coastal Surveyor. A video survey and bottom grab samples collected in December, 2007 indicated that the study area is comprised of rocky outcrops, flat sandy regions, gravel bottoms, and some gravel and sand ripples.
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Overview: The rapid warming of the Arctic and melting of Arctic sea and land ice will have ramifications around the globe. Shipping routes through an ice-free Northwest Passage in combination with modifications to ocean circulation and... more
Overview: The rapid warming of the Arctic and melting of Arctic sea and land ice will have ramifications around the globe. Shipping routes through an ice-free Northwest Passage in combination with modifications to ocean circulation and regional climate patterns linked to Arctic ice melt will affect trade, fisheries, tourism, coastal ecology, air and water quality, animal migration, and demographics not only in the Arctic but also in lower latitude coastal regions such as New England. With profound changes on the horizon, this is a critical opportunity for New England to prepare for uncertain yet inevitable economic and environmental impacts of Arctic change. In order to detect and respond to the challenges that New England will face as the nation’s eastern gateway to the Arctic, it will be necessary to modify traditional observational networks and models. This workshop pairs two of NSF’s 10 Big Ideas: Navigating the New Arctic and Growing Convergence Research at NSF. During this eve...
Research Interests: Marine Biology, Geography, Earth Sciences, Climate, Convergence, and 4 moreEnvironmental Sciences, Arctic, NNA, and NSF
The crash of SwissAir Flight 111, off Nova Scotia in September 1998, triggered one of the largest seabed search surveys in Canadian history. The primary search tools used were sidescan sonars (both conventional and focussed types) and... more
The crash of SwissAir Flight 111, off Nova Scotia in September 1998, triggered one of the largest seabed search surveys in Canadian history. The primary search tools used were sidescan sonars (both conventional and focussed types) and multibeam sonars. The processed search data needed to be distributed on a daily basis to other elements of the fleet for precise location of divers and other optical seabed search instruments (including laser linescan and ROV video). As a result of the glacial history of the region, many natural targets, similar in gross nature to aircraft debris were present. These included widespread linear bedrock outcrop patterns together with near ubiquitous glacial erratic boulders. Because of the severely broken-up nature of the remaining aircraft debris, sidescan imaging alone was often insufficient to unambiguously identify targets. The complementary attributes of higher resolution, but poorly located, sidescan imagery together with slightly lower resolution, ...
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Research Interests: Geology, Oceanography, Habitat, National Park, Fjord, and 4 moreGlacier, Bathymetry, Bay, and Benthic habitat
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Multibeam echosounder (MBES) systems have enjoyed recent popularity as a tool in bedform-migration studies due to their ability to produce high-resolution seafloor imagery with complete bottom coverage. Although shallow-water MBES systems... more
Multibeam echosounder (MBES) systems have enjoyed recent popularity as a tool in bedform-migration studies due to their ability to produce high-resolution seafloor imagery with complete bottom coverage. Although shallow-water MBES systems may achieve decimeter-scale data resolution, the use of MBES to successfully detect and quantify bedform migration on short time-scales (days to weeks) where the migration distance is relatively small (< 1 m) remains limited by positioning uncertainty. In this study we evaluate short-term bedform migration and sediment transport in a bedform field at the entrance to Portsmouth Harbor, New Hampshire, USA. Bedform dynamics over 24-hour and multi-day periods were determined from high-resolution bathymetry (0.25 m grid resolution) acquired with a Kongsberg EM3002D MBES system. Position, heading and attitude data were acquired with an Applanix POS/MV system with integrated real-time kinematic GPS correctors, providing a horizontal positioning uncerta...
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The chirp sonar is a calibrated wideband digital FM sonar that provides quantitative, high-resolution, low-noise subbottom data. In addition, it generates an acoustic pulse with special frequency domain weighting that provides nearly... more
The chirp sonar is a calibrated wideband digital FM sonar that provides quantitative, high-resolution, low-noise subbottom data. In addition, it generates an acoustic pulse with special frequency domain weighting that provides nearly constant resolution with depth. The chirp sonar was developed with the objective of remote acoustic classification of seafloor sediments. In addition to producing high-resolution images, the calibrated digitally recorded data are processed to estimate surficial reflection coefficients as well as a complete sediment acoustic impulse profile. In this paper, surficial sediments in Narragansett Bay, RI are used to provide ground truth for an acoustic model. Quantitative acoustic returns from the chirp sonar are used to estimate surficial acoustic impedance and to predict sediment properties. A robust acoustic sediment classification model that uses core samples to account for the local depositional environment has been developed. The model uses an estimate ...
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Research Interests: Geology, Oceanography, Holocene, Fjord, The cryosphere, and 3 moreGlacier, Ice Sheet, and Greenland ice sheet
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In the seismic reflection method, it is well known that seismic amplitude varies with the offset between the seismic source and detector and that this variation is a key to the direct determination of lithology and pore fluid content of... more
In the seismic reflection method, it is well known that seismic amplitude varies with the offset between the seismic source and detector and that this variation is a key to the direct determination of lithology and pore fluid content of subsurface strata. Based on this fundamental property, amplitude-versus-offset (AVO) analysis has been used successfully in the oil industry for the exploration and characterization of subsurface reservoirs. Multibeam sonars acquire acoustic backscatter over a wide range of incidence angles and the variation of the backscatter with the angle of incidence is an intrinsic property of the seafloor. Building on this analogy, we have adapted an AVO-like approach for the analysis of acoustic backscatter from multibeam sonar data. The analysis starts with the beam-by-beam time-series of acoustic backscatter provided by the multibeam sonar and then corrects the backscatter for seafloor slope (i.e. true incidence angle), time varying and angle varying gains, ...
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Deep sea canyons and seamounts are topographically complex features that are considered to be biological hotspots. Anthropogenic pressures related to climate change and human activities are placing the species that inhabit these features... more
Deep sea canyons and seamounts are topographically complex features that are considered to be biological hotspots. Anthropogenic pressures related to climate change and human activities are placing the species that inhabit these features at risk. Though studies have examined species composition on seamounts and canyons, few have compared communities between them, and even fewer studies have examined how species’ abundances correlate with environmental conditions or geomorphology. Consequently, this study compares species composition, community structure, and environmental variables between Northwest Atlantic continental margin canyons and seamounts along the New England Seamount Chain. Geoforms were also related to the occurrence of phyla and biodiversity. Overall, there was a significant difference in species composition between canyons and seamounts with sponges, corals, sea urchins and seastars contributing heavily to observed differences. Environmental conditions of temperature ...
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The processes controlling advance and retreat of outlet glaciers in fjords draining the Greenland Ice Sheet remain poorly known, undermining assessments of their dynamics and associated sea-level rise in a warming climate. Mass loss of... more
The processes controlling advance and retreat of outlet glaciers in fjords draining the Greenland Ice Sheet remain poorly known, undermining assessments of their dynamics and associated sea-level rise in a warming climate. Mass loss of the Greenland Ice Sheet has increased six-fold over the last four decades, with discharge and melt from outlet glaciers comprising key components of this loss. Here we acquired oceanographic data and multibeam bathymetry in the previously uncharted Sherard Osborn Fjord in northwest Greenland where Ryder Glacier drains into the Arctic Ocean. Our data show that warmer subsurface water of Atlantic origin enters the fjord, but Ryder Glacier’s floating tongue at its present location is partly protected from the inflow by a bathymetric sill located in the innermost fjord. This reduces under-ice melting of the glacier, providing insight into Ryder Glacier’s dynamics and its vulnerability to inflow of Atlantic warmer water.