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Map of Johns Hopkins Inlet study area. Johns Hopkins Inlet in Glacier Bay (top right inset), southeastern Alaska (top left inset). The standard false color composite image was created from a July 2013 Landsat 8 scene. Vegetated areas appear read and snow and ice appear in shades of white to grey. Individual image frames from the airborne survey along transect lines are plotted as small yellow squares.
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Tidewater glaciers are glaciers that terminate in, and calve icebergs into, the ocean. In addition
to the influence that tidewater glaciers have on physical and chemical oceanography, floating
icebergs serve as habitat for marine animals such as harbor seals (Phoca vitulina richardii).
The availability and spatial distribution of glacier ice in the...
Citations
... This is particularly advantageous for machine learning (ML) algorithms, as they generally perform better with a larger number of independent variables, albeit careful variable selection is required to avoid overfitting (Chen et al., 2020). In glaciology, OBIA has been applied to map debris-covered glaciers (Rastner et al., 2014;Robson et al., 2015), glacial lakes (Mitkari et al., 2017), and even iceberg detection (McNabb et al., 2016). Furthermore, the object-based approach has also been integrated with ML for studies of lacustrine icebergs (Podgórski and Petlicki, 2020), as well as glacier mapping in the Arctic (Ali et al., 2023) and the Pamir region (Lu et al., 2020). ...
In recent years, Chile has experienced an extraordinary drought that has had significant impacts on both the livelihoods of people and the environment, including the Andean glaciers. This study focuses on analyzing the surface processes of Universidad Glacier, a benchmark glacier for the Dry Andes. Multiple remote sensing datasets are used alongside a novel spectral index designed for mapping of rock material located on the glacier's surface. Our findings highlight the precarious state of the glacier, which serves as a crucial water source for the region. The glacier exhibits locally varied debris accumulation and margin retreat. The most significant impacts are observed on the tongue and secondary accumulation cirques, with the latter at risk of disappearing. The debris cover on the tongue is expanding, reaching higher elevations, and is accompanied by glacier retreat, especially at higher altitudes. The equilibrium line is rapidly shifting upglacier, although the mid-season snow cover still frequently reaches the 2013 equilibrium line, even in 2020. Changes in stream density on the glacier
tongue indicate an increased water supply in this area, likely due to enhanced melting of glacial ice. These observed processes align well with meteorological data obtained from reanalysis products. The behavior of dust and debris is influenced by precipitation amount, while the rate of retreat is linked to air temperature.
... Some of them have a coastal margin and terminate in a calving front, what establishes important differences with respect to glaciers with inland margin. Coastal glaciers calve icebergs into the ocean (McNabb et al., 2016). These glaciers greatly affect the physical and chemical characteristics of the sea to which they discharge (Garcia-Lopez et al., 2016). ...
... At present, analysis of glacial ice in tidewater glaciers is typically accomplished using high-resolution aerial images obtained from harbor seal surveys (Jansen et al., 2010(Jansen et al., , 2015. Images are captured by cameras mounted to the fuslage of a fixed-wing aircraft, which are flown at relatively high altitudes (approximately 305 m) along established transects, and surveys can be hindered by adverse weather conditions (McNabb et al., 2016;Womble et al., 2021). Advancements in computer imaging and technological innovations in remote sensing software, as well as reduced operational costs and increased capabilities of low-altitude (<20 m) unmanned aerial systems (UAS), have greatly advanced our abilities to map and evaluate environments and can be an alternative method for capturing aerial images (Watts et al., 2012). ...
Long‐term monitoring programs to evaluate climate‐driven changes to tidewater glaciers, an important habitat for harbor seals (Phoca vitulina) in Alaska, are primarily carried out by costly, weather‐dependent aerial surveys from fixed‐winged aircraft. Unmanned aerial systems (UAS) can be an alternative cost‐effective solution for gathering image data to quantify, monitor, and manage these habitats. However, there is a paucity of information related to the accuracy of using imagery collected by UAS for purposes of measuring floating icebergs. We evaluated the accuracy of using a UAS with a built‐in 20‐megapixel (MP) camera as well as a consumer‐grade digital 16‐MP camera to capture images of floating and stationary icebergs for the purpose of collecting vertical height measurements. Images (n = 869) were captured of simulated icebergs (cuboidal foam boxes, Cb) (n = 5) and real icebergs (n = 5) that were either grounded or floating. The mean error ratios (Ers) obtained were less than 10% and derived by comparing the mean calculated measurements of heights of Cb obtained from images captured by UAS with the physically measured heights of these Cb. The mean Er for height measurements of grounded icebergs (n = 4) and one floating iceberg was also less than 10%. Within an object–image distance range of 6–25 m, the cameras captured images that were suitable to accurately calculate the heights of floating and grounded objects, and drift or uncontrolled movement of the UAS caused by wind or temporary loss of GPS did not have any effect on measurement error. Our study provides substantial evidence of the accuracy associated with using images captured by UAS for measuring dimensions of structures positioned on either water or land surfaces. Ultimately, accurate surveys of glacial ice used by harbor seals will improve our understanding of the role of decreasing habitat in explaining population variability between different tidewater glaciers.
... To date, few studies have quantitatively addressed the relationships between harbor seals and ice habitat (e.g., Jansen et al., 2015), due in large part to the expansiveness and remote nature of tidewater glacier fjords as well as the dynamic nature of the ice habitat (Boveng et al., 2003;Bengtson et al., 2007). However, recent advances in survey and analytical methods allow for the systematic quantification of seals and ice using aerial photographic surveys which provide a permanent record McNabb et al., 2016). If tidewater glaciers continue to thin and retreat, the amount of ice habitat available for harbor seals may decrease and seals may spend more time in the water, use terrestrial sites, or move to other areas (Calambokidis et al., 1987;Womble et al., 2010;Hoover-Miller and Armato, 2018). ...
... (2) brash ice (%) defined as the percent of each scene that is ice smaller than 1.6 m 2 ; (3) water (%) of each scene that is water; (4) iceberg size (m 2 ) defined as average size of icebergs in each scene; and (5) distance to the terminus of the glacier (km) defined as the distance from the glacier calving face to the center point of each scene or image (McNabb et al., 2016). Minimum iceberg size was based on the premise that an iceberg of approximately 1.6 m 2 would be large enough to support a non-pup seal whereas icebergs smaller than 1.6 m 2 would be too small to support a seal and were thus classified as brash ice. ...
Tidewater glaciers calve icebergs into the marine environment which serve as pupping, molting, and resting habitat for some of the largest seasonal aggregations of harbor seals (Phoca vitulina richardii) in the world. Although they are naturally dynamic, advancing and retreating in response to local climatic and fjord conditions, most tidewater glaciers around the world are thinning and retreating. Climate change models predict continued loss of land-based ice with unknown impacts to organisms such as harbor seals that rely on glacier ice as habitat for critical life history events. To understand the impacts of changing ice availability on harbor seals, we quantified seasonal and annual changes in ice habitat in Johns Hopkins Inlet, a tidewater glacier fjord in Glacier Bay National Park in southeastern Alaska. We conducted systematic aerial photographic surveys (n = 55) of seals and ice during the pupping (June; n = 30) and molting (August; n = 25) periods from 2007 to 2014. Object-based image analysis was used to quantify the availability and spatial distribution of floating ice in the fjord. Multivariate spatial models were developed for jointly modeling stage-structured seal location data and ice habitat. Across all years, there was consistently more ice in the fjord during the pupping season in June than during the molting season in August, which was likely driven by seasonal variation in physical processes that influence the calving dynamics of tidewater glaciers. Non-pup harbor seals and ice were correlated during the pupping season, but this correlation was reduced during the molting season suggesting that harbor seals may respond to changes in habitat differently depending upon trade-offs associated with life history events, such as pupping and molting, and energetic costs and constraints associated with the events.
... The dark, debris-covered specimens, or ones with lines of sediment embedded in their faces stand out texturally against smooth water surface. OBIA has already been used successfully to study ocean-borne icebergs on radar [6] and high-resolution aerial optical [24] imagery, showing that the method is viable for iceberg research. ...
... To obtain these values, we compared the classified iceberg map to a manually created map. Such approach has been previously used [24], albeit our procedure is not identical to it. We divided the area of the lagoon without the proximal ice melange field into a grid of squares with 500 m long sides. ...
In the field of iceberg and glacier calving studies, it is important to collect comprehensive datasets of populations of icebergs. Particularly, calving of lake-terminating glaciers has been understudied. The aim of this work is to present an object-based method of iceberg detection and to create an inventory of icebergs located in a proglacial lagoon of San Quintín glacier, Northern Patagonia Icefield, Chile. This dataset is created using high-resolution WorldView-2 imagery and a derived DEM. We use it to briefly discuss the iceberg size distribution and area–volume scaling. Segmentation of the multispectral imagery produced a map of objects, which were classified with use of Random Forest supervised classification algorithm. An intermediate classification product was corrected with a ruleset exploiting contextual information and a watershed algorithm that was used
to divide multiple touching icebergs into separate objects. Common theoretical heavy-tail statistical distributions were tested as descriptors of iceberg area and volume distributions. Power law models were proposed for the area–volume relationship. The proposed method performed well over the open lake detecting correctly icebergs in all size bands except 5–15 m 2 where many icebergs were missed. A section of the lagoon with ice melange was not reliably mapped due to uniformity of the area in the imagery and DEM. The precision of the DEM limited the scaling effort to icebergs taller than 1.7 m and larger than 99 m 2 , despite the inventory containing icebergs as small as 4 m2 . The work demonstrates viability of object-based analysis for lacustrine iceberg detection and shows that the statistical properties of iceberg population at San Quintín glacier match those of populations produced by tidewater glaciers.
... Unfortunately, implementing and maintaining long-term monitoring to estimate the abundance and trend of harbor seals in tidewater glacier fjords is challenging due to the expansiveness and remote nature of these sites , Bengtson et al., 2007. In addition, the distribution and number of seals in fjords is dynamic Kelly, 1996, Womble andGende, 2013) and may change depending upon seal behavior, the availability and distribution of ice, and other environmental variables including prey distribution (Mathews and Pendleton, 2006, Womble et al., 2014, McNabb et al., 2016. Although harbor seals may travel widely during the post-breeding season, they exhibit a high degree of fidelity to tidewater glacier fjords during the pupping and molting seasons (Womble and Gende, 2013). ...
Long‐term monitoring for understanding status and trend of species of conservation concern is undeniably valuable, yet monitoring methods often evolve over time due to the development of new technology, fluctuations in funding, logistical constraints, and innovations in sampling methods or analytical approaches. Consequently, valuable insights into annual or decadal‐scale trends can be lost unless calibration between historical and current methods is developed. Glacier Bay National Park, in southeastern Alaska, hosts an important regional population of harbor seals, with the majority of seals pupping and molting on icebergs calved from a tidewater glacier in Johns Hopkins Inlet. Monitoring efforts to assess abundance and trends of harbor seals used counts of seals by shore‐based observers from 1992 to 2002, but transitioned to aerial photographic surveys in 2007 through 2017. To produce a rigorous long‐term evaluation of abundance and trends of harbor seals, we (1) conducted concurrent shore‐based counts and aerial photographic surveys in 2007 and 2008; (2) developed an analytical calibration between the two monitoring methods; (3) developed a haul‐out model to estimate the number of harbor seals in the water at the time of counts; and (4) estimated abundance and trends of harbor seals from 1992 to 2017 from the adjusted counts. Our calibration analysis revealed that during the pupping season in June, counts of harbor seals by observers from shore were consistently lower than counts from aerial surveys. During the molting season, counts by shore‐based observers were only slightly less than aerial photographic surveys, and there was an interaction between survey method and season. After calibrating methods, we found important decadal‐scale changes in trend. Over the 26‐yr period (1992–2017), the estimated trend was negative; however, trends computed for rolling 10‐yr time intervals showed steep and significant declines ending around 2011, with leveling off and possibly some subsequent recovery. The most recent shorter‐term (2013–2017) trends are negative again, rivaling the steepest decreases over the 26‐yr period. Our calibration between two monitoring methods improved continuity for long‐term monitoring for a species of conservation concern by taking advantage of new sampling methods and innovations in analytical approaches.
... Icebergs play an important role in polar oceans by providing habitat for marine mammals (Blundell et al., 2011;Lydersen et al., 2014), enhancing local primary production (Smith et al., 2007), facilitating sea ice growth with fresher meltwater (Merino et al., 2016), hindering advection of sea ice (Massom et al., 2001;Arrigo and van Dijken, 2003), and modifying water properties in the upper layer of the ocean within fjords (Moon et al., 2018), as well as in the open ocean (Gladstone et al., 2001;Silva et al., 2006). Icebergs also impact local weather conditions and their influence on ocean conditions are linked to carbon cycling and climate (Helly et al., 2011). ...
... The evaluation of height is not only necessary for classification, it is also crucial for assessing the three-dimensional surface morphology relevant to marine mammals (McNabb et al., 2016), the stability of the icebergs (Guttenberg et al., 2011), and expected keel depth (Enderlin et al., 2016). Moreover, iceberg morphology is related to the overall iceberg volume relevant to a number of important properties such as drift and decay (Hamley and Budd, 1986;Barker et al., 2004;Jacka and Giles, 2007;Crawford et al., 2018), freshwater contribution (Jacobs et al., 1992;Silva et al., 2006;Enderlin and Hamilton, 2014;Moon et al., 2018), and icebergs as a hazard (Bigg et al., 2018). ...
Icebergs in polar regions affect water salinity, alter
marine habitats, and impose serious hazards on maritime operations and
navigation. These impacts mainly depend on the iceberg volume, which remains
an elusive parameter to measure. We investigate the capability of TanDEM-X
bistatic single-pass synthetic aperture radar interferometry (InSAR) to
derive iceberg subaerial morphology and infer total volume. We cross-verify
InSAR results with Operation IceBridge (OIB) data acquired near Wordie Bay,
Antarctica, as part of the OIB/TanDEM-X Antarctic Science Campaign (OTASC).
While icebergs are typically classified according to size based on length or
maximum height, we develop a new volumetric classification approach for
applications where iceberg volume is relevant. For icebergs with heights
exceeding 5 m, we find iceberg volumes derived from TanDEM-X and OIB data
match within 7 %. We also derive a range of possible iceberg keel depths
relevant to grounding and potential impacts on subsea installations. These
results suggest that TanDEM-X could pave the way for future single-pass
interferometric systems for scientific and operational iceberg mapping and
classification based on iceberg volume and keel depth.
... Some of them have a coastal margin and terminate in a calving front, what establishes important differences with respect to glaciers with inland margin. Coastal glaciers calve icebergs into the ocean (McNabb et al., 2016). These glaciers greatly affect the physical and chemical characteristics of the sea to which they discharge (Garcia-Lopez et al., 2016). ...
Global warming is having a great impact on the Arctic region, due to the change of air temperature and precipitation. As a consequence, the glacial ice melts and englacial materials are being transported into the ocean. These substances can constitute a source of nutrients in food webs or, on the contrary, a source of contaminants. In this research seven marine Svalbard glaciers and their tidewater tongues were focused. This survey provides a first attempt comparing microbial communities from coastal and tidewater glaciers that reveal a hitherto unknown microbial diversity. A wider diversity was found in glaciers than in seawater samples. Glacier microorganisms mainly corresponded to the phylum Proteobacteria (48.8%), Bacteroidetes (29.1%) and Cyanobacteria (16.3%) (Figure 3A). Seawater microorganisms belonged to Bacteroidetes (40.3%), Actinobacteria (31.7%) and Proteobacteria (25.4%). Other phyla found such as Firmicutes, Thermi, Gemmatimonadetes, Verrucomicrobia, Nitrospirae, Chloroflexi, Planctomycetes, and Chlamydiae were less abundant. The distribution of microbial communities was affected in different extent by the concentration of nutrients (nitrogen nutrients, dissolved organic carbon and soluble reactive phosphorus) and by environmental parameters such as salinity. Nevertheless, the environmental variables did not influence in the distribution of the microbial communities as much as the concentration of nutrients did. Our results demonstrate an interchange between glacier and coastal microbial populations as well as the presence of some indicator species (i.e., Hymenobacter) as possible sentinels for bacterial transport between glaciers and their downstream seawaters. The consequence of this process could be the alteration of the water composition of the fiords producing serious consequences throughout the marine ecosystem and in the cycling of globally important elements.
... Aerial photographic images can provide several advantages over observer-based methods. Aerial photographic images provide a permanent record that is available for independent verification (Buckland et al. 2012), they can be used for automated detection (Conn et al. 2014, Seymour et al. 2017, and also allow for quantification of habitat covariates (McNabb et al. 2016). Photographic sampling methods also can be extended to unmanned aerial systems (UASs), which are relatively new platforms that can be used to quantify wildlife and their habitats (Hodgson et al. 2013, Moreland et al. 2015, Sweeney et al. 2015. ...
Sea otters (Enhydra lutris kenyoni) are an apex consumer in the North Pacific Ocean and are known to influence and structure nearshore marine communities. Sea otters were extirpated from southeastern Alaska prior to 1911 due to the commercial fur trade; however, approximately 400 sea otters were reintroduced to southeastern Alaska in the 1960s. By 1988, sea otters had expanded into lower Glacier Bay and the U.S. Geological Survey (USGS) began aerial survey monitoring efforts to monitor the colonization, distribution, and abundance of sea otters; these efforts continued through 2012.
Currently, sea otters are one of the most abundant marine mammals in the park.
In 2015, sea otters were identified as a vital sign by the National Park Service’s Southeast Alaska Network (SEAN) Monitoring Program due to their role as a keystone species in the nearshore marine ecosystem. The primary objectives of the monitoring program are to use contemporary field and analytical methods to monitor the abundance and spatial distribution of sea otters in Glacier Bay. A spatio-temporal statistical model representing current knowledge of sea otter abundance and distribution, including underlying ecological processes governing colonization dynamics in Glacier Bay, was constructed using multiple sources of data collected on sea otters between 1993 and 2012 and will accommodate future data to be collected via aerial photographic surveys. Specifically, a partial differential equation that incorporates knowledge of sea otter ecology and behavior including habitat preferences, maximum growth rates, and observations of sea otters was developed and embedded within a Bayesian hierarchical framework to accommodate uncertainty in the data collection process, the ecological process, and the model parameters. Development and testing of a new monitoring design and field methods were initiated in 2016 with a suite of objectives aimed at improving the safety of aerial surveys, the reliability of abundance and distribution information for informing park managers, and general program sustainability. Contemporary methods for obtaining digital imagery and counting sea otters from the imagery were developed to replace prior observer-based methods. Aerial photographic surveys will be conducted and digital imagery will be archived as a permanent record enabling independent verification of counts of sea otters and quantification of habitat covariates. New methods for estimating availability at the time of sampling utilize replicate counts, from repeated images of a group of sea otters, within an N-mixture model framework to estimate detection probability. The new monitoring design implements an iterative optimal dynamic sampling scheme to increase sampling efficiency, providing the most information from the data that can be collected affordably. The spatio-temporal model will be used to generate forecasts of sea otter abundance and associated uncertainty for subsequent monitoring periods. Forecasts then will be used as a template to select a set of survey transects that minimize the uncertainty in model-based forecasts of predicted abundance of sea otters. Optimal survey designs will be updated following each year data are collected and, therefore, are dynamic through time. A set of random transects also will be selected to supplement, validate, and compare abundance estimates of sea otters among sampling approaches. Reallocation of effort among survey types will be considered in the future as another means to optimize program performance and efficiency.
The combination of using (1) aerial photographs for collecting data, (2) advanced and flexible statistical models that incorporate our understanding of the ecological system, permitting rigorous estimates of occupancy, abundance, and colonization dynamics, and (3) a sampling framework that explicitly links our statistical model and future data to be collected, will improve monitoring efficiency, and our ecological understanding of sea otters in Glacier Bay.
Icebergs in proglacial fjords serve as pupping, resting and molting habitat for some of the largest seasonal aggregations of harbor seals ( Phoca vitulina richardii ) in Alaska. One of the largest aggregations in Southeast Alaska occurs in Johns Hopkins Inlet, Glacier Bay National Park, where up to 2000 seals use icebergs produced by Johns Hopkins Glacier. Like other advancing tidewater glaciers, the advance of Johns Hopkins Glacier over the past century has been facilitated by the growth and continual redistribution of a submarine end moraine, which has limited mass losses from iceberg calving and submarine melting and enabled glacier thickening by providing flow resistance. A 15-year record of aerial surveys reveals (i) a decline in iceberg concentrations concurrent with moraine growth and (ii) that the iceberg size distributions can be approximated as power law distributions, with relatively little variability and no clear trends in the power law exponent despite large changes in ice fluxes over seasonal and interannual timescales. Together, these observations suggest that sustained tidewater glacier advance should typically be associated with reductions in the number of large, habitable icebergs, which may have implications for harbor seals relying on iceberg habitat for critical life-history events.
