scholarly journals A Modified Approach of Extracting Landfast Ice Edge Based on Sentinel-1A InSAR Coherence Image in the Gulf of Bothnia

2021 ◽  
Vol 9 (10) ◽  
pp. 1076
Author(s):  
Zhiyong Wang ◽  
Zihao Wang ◽  
Hao Li ◽  
Ping Ni ◽  
Jian Liu
Keyword(s):  
Median Filter ◽  
Reference Method ◽  
Radar Data ◽  
Landfast Ice ◽  
Gulf Of Bothnia ◽  
Ice Edge ◽  
Image Pairs ◽  
Edge Based ◽  
The Baltic ◽  
Local Edge

Landfast ice is an integral component of the coastal ecosystem. Extracting the edge and mapping the extent of landfast ice are one of the main methods for studying ice changes. In this work, a standardized process for extracting landfast ice edge in the Baltic Sea using the InSAR coherence image is established with Sentinel-1 radar data and InSAR technology. A modified approach combining multiscale segmentation and morphological erosion is then proposed to provide a reliable way to extract landfast ice edge. Firstly, the coherence image is obtained using InSAR technology. Then, the edge is separated and extracted with the modified approach. The modified approach is essentially a four-step procedure involving image segmentation, median filter, morphological erosion, and rejection of small patches. Finally, the full extent of landfast ice can be obtained using floodfill algorithm. Multiple InSAR image pairs of Sentinel-1A acquired from 2018 to 2019 are utilized to successfully extract the landfast ice edge in the Gulf of Bothnia. The results show that the landfast ice edge and the extents obtained by the proposed approach are visually consistent with those shown in the ice chart issued by the Swedish Meteorological and Hydrological Institute (SMHI) over a coastline length of 345 km. The mean distance between land–water boundary and the coastline issued by the National Oceanic and Atmospheric Administration (NOAA) is 109.1 m. The modified approach obviously preserves more details in local edge than the reference method. The experimental results show that the modified approach proposed in this paper can extract the edge and map the extent of landfast ice more accurately and quickly, and is therefore expected to contribute to the further understanding and analyzing the changes of landfast ice in the future.

scholarly journals Ice-edge detection from Japanese C-band radar and high-frequency radar coastal stations

2013 ◽  
Vol 54 (62) ◽  
pp. 59-64 ◽  
Author(s):  
K. Shirasawa ◽  
N. Ebuchi ◽  
M. Leppäranta ◽  
T. Takatsuka
Keyword(s):  
Sea Ice ◽  
Edge Detection ◽  
High Frequency ◽  
Open Water ◽  
Radar Data ◽  
Hf Radar ◽  
Sea Surface ◽  
Geometrical Structures ◽  
Overlapping Data ◽  
Ice Edge

AbstractA C-band sea-ice radar (SIR) network system was operated to monitor the sea-ice conditions off the Okhotsk Sea coast of northern Hokkaido, Japan, from 1969 to 2004. The system was based on three radar stations, which were capable of continuously monitoring the sea surface as far as 60 km offshore along a 250 km long coastal section. In 2004 the SIR system was closed down and a sea surface monitoring programme was commenced using high-frequency (HF) radar; this system provides information on surface currents in open-water conditions, while areas with ‘no signal’ can be identified as sea ice. The present study compares HF radar data with SIR data to evaluate their feasibility for sea-ice remote sensing. The period of overlapping data was 1.5 months. The results show that HF radar information can be utilized for ice-edge mapping although it cannot fully compensate for the loss of the SIR system. In particular, HF radar does not provide ice concentration, ice roughness and geometrical structures or ice kinematics. The probability of ice-edge detection by HF radar was 0.9 and the correlation of the ice-edge distance between the radars was 0.7.

scholarly journals Interactions between grey seal (Halichoerus grypus), Atlantic salmon (Salmo salar), and harvest controls on the salmon fishery in the Gulf of Bothnia

2006 ◽  
Vol 63 (5) ◽  
pp. 936-945 ◽  
Author(s):  
P. Jounela ◽  
P. Suuronen ◽  
R.B. Millar ◽  
M-L. Koljonen
Keyword(s):  
Atlantic Salmon ◽  
Baltic Sea ◽  
Monte Carlo Analysis ◽  
Grey Seal ◽  
Fishing Gears ◽  
Gulf Of Bothnia ◽  
Spawning Run ◽  
The Baltic ◽  
Major Factors ◽  
Salmon Fishery

Abstract Interactions between grey seal, Atlantic salmon, and harvest controls on the salmon fishery in the Gulf of Bothnia, northern Baltic Sea, were investigated for the period 1999–2003. We assessed the effects of seal-induced catch losses (fish damaged or eaten by seals in the fishing gears) and harvest restrictions (delayed sequential opening of the fishery from south to north) on the Finnish coastal salmon catch and on escapement of salmon into the Tornionjoki River, the major breeding ground of the species in the Baltic Sea. Commercial logbook data on catches and seal-induced catch losses were used in a stochastic Monte Carlo analysis, indicating that mainly because of the stricter harvest controls enforced in 1996 and 1997, the average annual spawning run abundance that approached the Finnish coastal area increased by ca. 56 700 fish between 2000 and 2002. However, these fish were caught increasingly in the northern Gulf of Bothnia (Management Areas, MAs, 3 and 4), and relatively few salmon escaped into the Tornionjoki River. The landings in MAs 3 and 4 increased by 57% and 144%, respectively, whereas in the southern Gulf of Bothnia (MA 1), landings decreased by 23%. Over the five years of the study, seal-induced catch losses in MA 1 ranged from 24% to 29% of the total catch, whereas in MAs 2, 3, and 4 it ranged from 3% to 16%. The analysis suggests, however, that in MA 1 the regulation-induced catch losses were even higher than seal-induced catch losses, indicating that the salmon fishery was being impacted by both major factors. To increase escapement into the river and potentially to increase the future wild salmon catch, the opening of the harvest in the northernmost MAs should be delayed. Seal-induced catch losses should be reduced by extensive introduction of seal-safe fishing gears and by sustainable control of the grey seal population.

The Spreading of a Buoyant Plume Beneath a Landfast Ice Cover

2015 ◽  
Vol 45 (2) ◽  
pp. 478-494 ◽  
Author(s):  
Jeremy L. Kasper ◽  
Thomas J. Weingartner
Keyword(s):  
Vertical Mixing ◽  
Ice Cover ◽  
Ocean Modeling ◽  
Freshwater Flux ◽  
Buoyant Plume ◽  
Regional Ocean Modeling System ◽  
Case Subject ◽  
Landfast Ice ◽  
Free Case ◽  
Ice Edge

AbstractIdealized numerical simulations using the Regional Ocean Modeling System demonstrate the effects of an immobile landfast ice cover that is frictionally coupled to an underice buoyant plume established by river discharge. The discharge rapidly increases and decreases over a 30-day period and has a maximum of 6000 m3 s−1. This study examined the response to a landfast ice cover of 26-km width and one that encompasses the entire shelf width. The model setting mimics spring conditions on the Alaskan Beaufort Sea (ABS) shelf. In comparison with the ice-free case subject to the same discharge scenario, underice plumes are broader and deeper, and the downwave freshwater flux is substantially decreased and delayed. Multiple anticyclonic bulges form in the ice-free case, but only a single, large bulge forms when ice is present. These differences are because of the frictional coupling between the ice and plume, which results in an Ekman-like underice boundary layer, a subsurface velocity maximum, and frictional shears that enhance vertical mixing and entrainment. For a partially ice-covered shelf, the plume spreads across the ice edge to form a swift, buoyant, ice-edge jet, whose width accords with the scale of Yankovsky and Chapman for a surface-advected plume. For a fully ice-covered shelf, the buoyant water spreads 60 km offshore over a 30-day period. For a steady discharge of 6000 m3 s−1 and a completely ice-covered shelf, the plume spreads offshore at a rate of ~1.5 km day−1 and extends ~95 km offshore after 60 days.

Sustaining ecological and subsistence functions in conservation areas: eider habitat and access by Native hunters along landfast ice

2018 ◽  
Vol 45 (4) ◽  
pp. 361-369 ◽  
Author(s):  
JAMES R. LOVVORN ◽  
AARIEL R. ROCHA ◽  
ANDREW H. MAHONEY ◽  
STEPHEN C. JEWETT
Keyword(s):  
Chukchi Sea ◽  
Open Water ◽  
The Arctic ◽  
Cash Income ◽  
Migration Route ◽  
Conservation Areas ◽  
Subsistence Hunting ◽  
Industrial Activities ◽  
Landfast Ice ◽  
Ice Edge

SUMMARYIn the Arctic, rapid climate change has kindled efforts to delineate and project the future of important habitats for marine birds and mammals. These animals are vital to subsistence economies and cultures, so including the needs of both animals and hunters in conservation planning is key to sustaining social-ecological systems. In the northeast Chukchi Sea, a nearshore corridor of open water is a major spring migration route for half a million eider ducks that are hunted along the landfast ice. Zoning areas for industrial activities or conservation should consider both eider habitat and hunter access to those habitats from the variable ice edge. Based on benthic sampling in 2010‒2012, a model of eider foraging energetics and satellite data on ice patterns in April and May 1997‒2011, we mapped the range of positions of the landfast ice edge relative to a given dispersion of habitat suitable for eider feeding. In some sectors, feeding areas were too limited or too far from landfast ice to provide regular hunting access. In other sectors, overlap of the ice edge with eider feeding habitat was quite variable, but often within a consistent geographic range. Areas accessible to hunters were a small fraction of total eider habitat, so areas adequate for conserving eiders would not necessarily include areas that meet the hunters’ needs. These results can inform spatial planning of industrial activities that yield cash income critical to subsistence hunting in less developed locations. Our study provides an approach for mapping ‘subsistence conservation areas’ throughout the Arctic and an example for such efforts elsewhere.

scholarly journals OBJECT CONTOUR COMPLETION BY COMBINING OBJECT RECOGNITION AND LOCAL EDGE CUES

2017 ◽  
Author(s):  
Kar Seng Loke
Keyword(s):  
Optimization Procedure ◽  
Specific Information ◽  
Top Down ◽  
Bottom Up ◽  
Object Contour ◽  
Contour Feature ◽  
Edge Based ◽  
Local Edge ◽  
Initial Object ◽  
Contour Completion

We developed a top-down and bottom-up segmentation ofobjects using shape contours through a two-stage procedure. First, the object was identified using an edge-based contour feature and then the object contour was obtained using a constraint optimization procedure based on the results from the earlier identified contours. The initial object detection provides object category specific information for the contour completion to be effected. We argue that top-down bottom-up interaction architecture has plausible neurological correlates. This method has an advantage in that it does not require learning boundaries with large datasets.  

scholarly journals Processing methodology for the ITS_LIVE Sentinel-1 ice velocity product

2021 ◽  
Author(s):  
Yang Lei ◽  
Alex S. Gardner ◽  
Piyush Agram
Keyword(s):  
Ice Sheet ◽  
Radar Data ◽  
Electron Content ◽  
Image Pair ◽  
Total Electron ◽  
Velocity Inversion ◽  
Slant Range ◽  
Ice Velocity ◽  
Image Pairs ◽  
Offset Tracking

Abstract. The NASA MEaSUREs Inter-mission Time Series of Land Ice Velocity and Elevation (ITS_LIVE) project seeks to accelerate understanding of critical glaciers and ice sheet processes by providing researchers with global, low-latency, comprehensive and state-of-the-art records of surface velocities and elevations as observed from space. Here we describe the image-pair ice velocity product and processing methodology for ESA Sentinel-1 radar data. We demonstrate improvements to the core processing algorithm for dense offset tracking, “autoRIFT”, that provides finer resolution and higher accuracy data products with improved computational efficiency when compared to earlier versions. A novel calibration is applied to the data to correct for Sentinel-1A/B subswath- and full swath-dependent geolocation errors caused by systematic issues with the instruments. Sentinel-1’s C-band images are affected by variations in the total electron content of the ionosphere that results in large velocity errors in the azimuth (along-track) direction. To reduce these effects slant-range (line-of-sight or LOS) velocities are used and accompanied by LOS parameters that support map coordinate (x/y) velocity inversion from ascending and descending slant-range offset measurements, as derived from 2 image-pairs. The described product and methods comprise the MEaSUREs ITS_LIVE Sentinel-1 Image-Pair Glacier and Ice Sheet Surface Velocities: Version 2 (https://its-live.jpl.nasa.gov).

scholarly journals SEA LEVEL VARIATIONS IN THE GULF OF BOTHNIA

1973 ◽  
Vol 4 (1) ◽  
pp. 41-53 ◽  
Author(s):  
EUGENIE LISITZIN
Keyword(s):  
Baltic Sea ◽  
Sea Level ◽  
Water Volume ◽  
Tide Gauges ◽  
The Baltic Sea ◽  
Land Uplift ◽  
Gulf Of Bothnia ◽  
Sea Level Variations ◽  
The Baltic

An attempt is made to compute the sea level variations in the Gulf of Bothnia, which is isolated by islands and thresholds from the Baltic Sea proper. Observations from tide gauges during the 30-year period 1931–1960 were used. The effect of land uplift was taken into consideration. The maximum annual deviation in water volume from the long-term mean corresponded to 20.74 km3..

scholarly journals Operational Service for Mapping the Baltic Sea Landfast Ice Properties

2020 ◽  
Vol 12 (24) ◽  
pp. 4032
Author(s):  
Marko Mäkynen ◽  
Juha Karvonen ◽  
Bin Cheng ◽  
Mwaba Hiltunen ◽  
Patrick B. Eriksson
Keyword(s):  
Sea Ice ◽  
Baltic Sea ◽  
Prediction Models ◽  
Winter Season ◽  
Free Access ◽  
The Baltic Sea ◽  
Usable Information ◽  
Landfast Ice ◽  
Sar Imagery ◽  
The Baltic

The Baltic Sea is partly covered by sea ice in every winter season. Landfast ice (LFI) on the Baltic Sea is a place for recreational activities such as skiing and ice fishing. Over thick LFI ice roads can be established between mainland and islands to speed up transportation compared to the use of ferries. LFI also allows transportation of material to or from islands without piers for large ships. For all these activities, information on LFI extent and sea ice thickness, snow thickness and degree of ice deformation on LFI is very important. We generated new operational products for these LFI parameters based on synthetic aperture radar (SAR) imagery and existing products and prediction models on the Baltic Sea ice properties. The products are generated daily and have a 500 m pixel size. They are visualized in a web-portal titled “Baltic Sea landfast ice extent and thickness (BALFI)” which has free access. The BALFI service was started in February 2019. Before the BALFI service, information on the LFI properties in fine scale (<1 km) was not available from any single source or product. We studied the accuracy and quality of the BALFI products for the ice season 2019–2020 using ice charts and in-situ coastal ice station data. We suggest that the current products give usable information on the Baltic LFI properties for various end-users. We also identify some topics for the further development of the BALFI products.

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