scholarly journals The effect of changing sea ice on the vulnerability of Arctic coasts

2014 ◽  
Vol 8 (3) ◽  
pp. 2277-2329 ◽  
Author(s):  
K. R. Barnhart ◽  
I. Overeem ◽  
R. S. Anderson
Keyword(s):  
Sea Ice ◽  
Water Level ◽  
Coastal Erosion ◽  
Extreme Values ◽  
Open Water ◽  
Water Levels ◽  
The Arctic ◽  
Sea Ice Concentration ◽  
Ice Edge ◽  
Sea Ice Edge

Abstract. Shorefast sea ice prevents the interaction of the land and the ocean in the Arctic winter and influences this interaction in the summer by governing the fetch. In many parts of the Arctic the sea-ice-free season is increasing in duration, and the summertime sea ice extents are decreasing. Sea ice provides a first order control on the vulnerability of Arctic coasts to erosion, inundation, and damage to settlements and infrastructure. We ask how the changing sea ice cover has influenced coastal erosion over the satellite record. First, we present a pan-Arctic analysis of satellite-based sea ice concentration specifically along the Arctic coasts. The median length of the 2012 open water season in comparison to 1979 expanded by between 1.5 and 3-fold by Arctic sea sector which allows for open water during the stormy Arctic fall. Second, we present a case study of Drew Point, Alaska, a site on the Beaufort Sea characterized by ice-rich permafrost and rapid coastal erosion rates where both the duration of the sea ice free season and distance to the sea ice edge, particularly towards the northwest, has increased. At Drew Point, winds from the northwest result in increased water levels at the coast and control the process of submarine notch incision, the rate-limiting step of coastal retreat. When open water conditions exist, the distance to the sea ice edge exerts control on the water level and wave field through its control on fetch. We find that the extreme values of water level set-up have increased, consistent with increasing fetch.

scholarly journals The effect of changing sea ice on the physical vulnerability of Arctic coasts

2014 ◽  
Vol 8 (5) ◽  
pp. 1777-1799 ◽  
Author(s):  
K. R. Barnhart ◽  
I. Overeem ◽  
R. S. Anderson
Keyword(s):  
Sea Ice ◽  
Water Level ◽  
Coastal Erosion ◽  
Open Water ◽  
Water Levels ◽  
The Arctic ◽  
Ocean Water ◽  
Physical Vulnerability ◽  
Ice Edge ◽  
Sea Ice Edge

Abstract. Sea ice limits the interaction of the land and ocean water in the Arctic winter and influences this interaction in the summer by governing the fetch. In many parts of the Arctic, the open-water season is increasing in duration and summertime sea-ice extents are decreasing. Sea ice provides a first-order control on the physical vulnerability of Arctic coasts to erosion, inundation, and damage to settlements and infrastructures by ocean water. We ask how the changing sea-ice cover has influenced coastal erosion over the satellite record. First, we present a pan-Arctic analysis of satellite-based sea-ice concentration specifically along the Arctic coasts. The median length of the 2012 open-water season, in comparison to 1979, expanded by between 1.5 and 3-fold by Arctic Sea sector, which allows for open water during the stormy Arctic fall. Second, we present a case study of Drew Point, Alaska, a site on the Beaufort Sea, characterized by ice-rich permafrost and rapid coastal-erosion rates, where both the duration of the open-water season and distance to the sea-ice edge, particularly towards the northwest, have increased. At Drew Point, winds from the northwest result in increased water levels at the coast and control the process of submarine notch incision, the rate-limiting step of coastal retreat. When open-water conditions exist, the distance to the sea ice edge exerts control on the water level and wave field through its control on fetch. We find that the extreme values of water-level setup have increased consistently with increasing fetch.

scholarly journals Retrieval of Summer Sea Ice Concentration in the Pacific Arctic Ocean from AMSR2 Observations and Numerical Weather Data Using Random Forest Regression

2021 ◽  
Vol 13 (12) ◽  
pp. 2283
Author(s):  
Hyangsun Han ◽  
Sungjae Lee ◽  
Hyun-Cheol Kim ◽  
Miae Kim
Keyword(s):  
Random Forest ◽  
Sea Ice ◽  
Arctic Ocean ◽  
Open Water ◽  
The Arctic ◽  
Atmospheric Effects ◽  
Sea Ice Concentration ◽  
Air Temperatures ◽  
The Pacific ◽  
Ice Concentration

The Arctic sea ice concentration (SIC) in summer is a key indicator of global climate change and important information for the development of a more economically valuable Northern Sea Route. Passive microwave (PM) sensors have provided information on the SIC since the 1970s by observing the brightness temperature (TB) of sea ice and open water. However, the SIC in the Arctic estimated by operational algorithms for PM observations is very inaccurate in summer because the TB values of sea ice and open water become similar due to atmospheric effects. In this study, we developed a summer SIC retrieval model for the Pacific Arctic Ocean using Advanced Microwave Scanning Radiometer 2 (AMSR2) observations and European Reanalysis Agency-5 (ERA-5) reanalysis fields based on Random Forest (RF) regression. SIC values computed from the ice/water maps generated from the Korean Multi-purpose Satellite-5 synthetic aperture radar images from July to September in 2015–2017 were used as a reference dataset. A total of 24 features including the TB values of AMSR2 channels, the ratios of TB values (the polarization ratio and the spectral gradient ratio (GR)), total columnar water vapor (TCWV), wind speed, air temperature at 2 m and 925 hPa, and the 30-day average of the air temperatures from the ERA-5 were used as the input variables for the RF model. The RF model showed greatly superior performance in retrieving summer SIC values in the Pacific Arctic Ocean to the Bootstrap (BT) and Arctic Radiation and Turbulence Interaction STudy (ARTIST) Sea Ice (ASI) algorithms under various atmospheric conditions. The root mean square error (RMSE) of the RF SIC values was 7.89% compared to the reference SIC values. The BT and ASI SIC values had three times greater values of RMSE (20.19% and 21.39%, respectively) than the RF SIC values. The air temperatures at 2 m and 925 hPa and their 30-day averages, which indicate the ice surface melting conditions, as well as the GR using the vertically polarized channels at 23 GHz and 18 GHz (GR(23V18V)), TCWV, and GR(36V18V), which accounts for atmospheric water content, were identified as the variables that contributed greatly to the RF model. These important variables allowed the RF model to retrieve unbiased and accurate SIC values by taking into account the changes in TB values of sea ice and open water caused by atmospheric effects.

scholarly journals Sea-ice edge is more important than closer open water access for foraging Adélie penguins: evidence from two colonies

2020 ◽  
Vol 640 ◽  
pp. 215-230
Author(s):  
C Michelot ◽  
A Kato ◽  
T Raclot ◽  
K Shiomi ◽  
P Goulet ◽  
...  
Keyword(s):  
Sea Ice ◽  
Environmental Changes ◽  
Early Stage ◽  
Open Water ◽  
Gps Tracking ◽  
Ice Edge ◽  
Sea Ice Edge ◽  
Study Sites ◽  
The Impact ◽  
Adélie Penguins

Sentinel species, like Adélie penguins, have been used to assess the impact of environmental changes, and their link with sea ice has received considerable attention. Here, we tested if foraging Adélie penguins from 2 colonies in East Antarctica target the distant sea-ice edge or take advantage of closer open waters that are readily available near their colony. We examined the foraging behaviour of penguins during the incubation trips of females in 2016 and males in 2017, using GPS tracking and diet data in view of daily sea-ice data and bathymetry. In 2016-2017, sea-ice cover was extensive during females’ trips but flaw leads and polynyas were close to both study sites. Sea ice receded rapidly during males’ trips in 2017-2018. Despite close open water near both colonies in both years, females and males preferentially targeted the continental slope and the sea-ice edge to forage. In addition, there was no difference in the diet of penguins from both colonies: all penguins fed mostly on Antarctic krill and males also foraged on Antarctic silverfish. Our results highlight the importance of the sea-ice edge for penguins, an area where food abundance is predictable. It is likely that resource availability was not sufficient in closer open water areas at such an early stage in the breeding season. The behaviours displayed by the penguins from both colonies were similar, suggesting a common behaviour across colonies in Terre Adélie, although additional sites would be necessary to confirm this hypothesis.

scholarly journals The impact of melt ponds on summertime microwave brightness temperatures and sea ice concentrations

2016 ◽  
Author(s):  
S. Kern ◽  
A. Rösel ◽  
L. T. Pedersen ◽  
N. Ivanova ◽  
R. Saldo ◽  
...  
Keyword(s):  
Sea Ice ◽  
Open Water ◽  
The Arctic ◽  
Sea Ice Concentration ◽  
Water Fraction ◽  
Microwave Brightness Temperature ◽  
Ice Melt ◽  
Melt Ponds ◽  
Retrieval Algorithms ◽  
The Impact

Abstract. The sea ice concentration (SIC) derived from satellite microwave brightness temperature (TB) data are known to be less accurate during summer melt conditions – in the Arctic Ocean primarily because of the impact of melt ponds on sea ice. Using data from June to August 2009, we investigate how TBs and SICs vary as a function of the ice surface fraction (ISF) computed from open water fraction and melt pond fraction both derived from satellite optical reflectance data. SIC is computed from TBs using a set of eight different retrieval algorithms and applying a consistent set of tie points. We find that TB values change during sea ice melt non-linearly and not monotonically as a function of ISF for ISF of 50 to 100 %. For derived parameters such as the polarization ratio at 19 GHz the change is monotonic but substantially smaller than theoretically expected. Changes in ice/snow radiometric properties during melt also contribute to the TB changes observed; these contributions are functions of frequency and polarization and have the potential to partly counter-balance the impact of changing ISF on the observed TBs. All investigated SIC retrieval algorithms overestimate ISF when using winter tie points. The overestimation varies among the algorithms as a function of ISF such that the SIC retrieval algorithms could be categorized into two different classes. These reveal a different degree of ISF overestimation at high ISF and an opposite development of ISF over-estimation as ISF decreases. For one class, correlations between SIC and ISF are ≥ 0.85 and the associated linear regression lines suggest an exploitable relationship between SIC and ISF if reliable summer sea ice tie points can be established. This study shows that melt ponds are interpreted as open water by the SIC algorithms, while the concentration of ice between the melt ponds is in general being overestimated. These two effects may cancel each other out and thus produce seemingly correct SIC for the wrong reasons. This cancelling effect will in general only be "correct" at one specific value of MPF. Based on our findings we recommend to not correct SIC algorithms for the impact of melt ponds as this seems to violate physical principles. Users should be aware that the SIC algorithms available at the moment retrieve a combined parameter presented by SIC in winter and ISF in summer.

scholarly journals Perspectives on future sea ice and navigability in the Arctic

2021 ◽  
Vol 15 (12) ◽  
pp. 5473-5482
Author(s):  
Jinlei Chen ◽  
Shichang Kang ◽  
Wentao Du ◽  
Junming Guo ◽  
Min Xu ◽  
...  
Keyword(s):  
Sea Ice ◽  
Coupled Model ◽  
Open Water ◽  
Circulation Pattern ◽  
The Arctic ◽  
Sea Ice Concentration ◽  
Sea Ice Extent ◽  
Sea Ice Thickness ◽  
Transportation Accessibility ◽  
Decadal Rate

Abstract. The retreat of sea ice has been found to be very significant in the Arctic under global warming. It is projected to continue and will have great impacts on navigation. Perspectives on the changes in sea ice and navigability are crucial to the circulation pattern and future of the Arctic. In this investigation, the decadal changes in sea ice parameters were evaluated by the multi-model from the Coupled Model Inter-comparison Project Phase 6, and Arctic navigability was assessed under two shared socioeconomic pathways (SSPs) and two vessel classes with the Arctic transportation accessibility model. The sea ice extent shows a high possibility of decreasing along SSP5-8.5 under current emissions and climate change. The decadal rate of decreasing sea ice extent will increase in March but decrease in September until 2060, when the oldest ice will have completely disappeared and the sea ice will reach an irreversible tipping point. Sea ice thickness is expected to decrease and transit in certain parts, declining by −0.22 m per decade after September 2060. Both the sea ice concentration and volume will thoroughly decline at decreasing decadal rates, with a greater decrease in volume in March than in September. Open water ships will be able to cross the Northern Sea Route and Northwest Passage between August and October during the period from 2045 to 2055, with a maximum navigable percentage in September. The time for Polar Class 6 (PC6) ships will shift to October–December during the period from 2021 to 2030, with a maximum navigable percentage in October. In addition, the central passage will be open for PC6 ships between September and October during 2021–2030.

scholarly journals Validation metrics for ice edge position forecasts

2019 ◽  
Author(s):  
Arne Melsom ◽  
Cyril Palerme ◽  
Malte Müller
Keyword(s):  
Sea Ice ◽  
Quality Assessment ◽  
Product Quality ◽  
Information Quality ◽  
Concentration Field ◽  
Essential Element ◽  
The Arctic ◽  
Sea Ice Concentration ◽  
Ice Edge

Abstract. The ice edge is a simple quantity in the form of a line that can be derived from a spatially varying sea ice concentration field. Due to its long history and relevance for operations in the Arctic, the position of the ice edge should be an essential element in any system that is designed to monitor or provide forecasts for the physical state of the Arctic Ocean and adjacent ocean regions. Like for all components of monitoring and forecast products, users need to complement information about the ice edge position with the expected accuracy of the data or model results. Such information is traditionally available as a set of metrics that provide a concentrated assessment of the information quality. In this study we provide a survey of metrics that are presently included in the product quality assessment of the CMEMS Arctic Marine Forecasting Center sea-ice edge position forecast. We show that when ice edge results from different products are compared, mismatching results for polynya and local freezing at the coasts of continents and archipelagos have a large impact on the quality assessment. Such situations, which occur regularly in the products we examine, have not previously properly been acknowledged when a set of metrics for the quality of ice edge position results have been constructed. We examine the quality of ice edge forecasts using a total of 17 metrics for the ice edge position. These metrics are analyzed in synthetic examples, in selected cases of actual forecasts, and for a full year of weekly forecast bulletins. Using necessity and simplicity of information as a guideline, we recommend using a set of four metrics that sheds light on the various aspects of product quality that we consider. Moreover, any user is expected to be interested in a limited part of the geographical domain, so metrics derived as domain-wide integrated quantities may be of limited value. Consequently, we recommend that metrics are also made available for appropriate set of subdomains. Furthermore, we find that the metrics' decorrelation time scales are much longer than the present forecast range. Hence our final recommendation is to include depictions of gridded mismatching of ice edge positions using maps for the integrated ice edge error.

scholarly journals Food web structure of the epibenthic community at the sea ice edge in Baffin Bay, Canada

2018 ◽  
Author(s):  
Gustavo Yunda-Guarin ◽  
Philippe Archambault ◽  
Guillaume Massé ◽  
Christian Nozais
Keyword(s):  
Climate Change ◽  
Sea Ice ◽  
Food Web ◽  
Trophic Levels ◽  
The Arctic ◽  
Feeding Guilds ◽  
Food Web Structure ◽  
Baffin Bay ◽  
Ice Edge ◽  
Sea Ice Edge

In polar areas, the pelagic-benthic coupling plays a fundamental role in ensuring organic matter flow across depths and trophic levels. Climate change impacts the Arctic’s physical environment and ecosystem functioning, affecting the sequestration of carbon, the structure and efficiency of the benthic food web and its resilience.In the Arctic Ocean, highest atmospheric warming tendencies (by ~0.5°C) occur in the east of Baffin Bay making this area an ideal site to study the effects of climate change on benthic communities. We sampled epibenthic organisms at 13 stations bordering the sea ice between June and July 2016. The epibenthic taxonomic composition was identified and grouped by feeding guilds. Isotopic signatures (δ13C - δ15N), trophic levels and trophic separation and redundancy were measured and quantified at each station. In the light of the results obtained, the stability of the benthic community in the Baffin Bay at the sea ice edge is discussed.

Biomarker distributions in surface sediments of the northern Barents Sea: a basis for accurate palaeo sea-ice reconstructions

2020 ◽  
Author(s):  
Anna J. Pienkowski ◽  
Katrine Husum ◽  
Simon Belt ◽  
Lukas Smik
Keyword(s):  
Sea Ice ◽  
Surface Sediments ◽  
Barents Sea ◽  
General Pattern ◽  
Environmental Parameters ◽  
Sea Ice Concentration ◽  
Marine Surface ◽  
Ice Edge ◽  
Spring Sea Ice ◽  
Sea Ice Edge

<p>An understanding of modern sea-ice proxy distributions relative to measured environmental parameters underpins accurate palaeo reconstructions necessary for correct future projections. We here present new data on highly-branched isoprenoid (HBI) lipid biomarkers produced by sea-ice diatoms (IP<sub>25</sub>, IPSO<sub>25</sub>) and phytoplankton (HBI III, HBI IV) in marine surface sediments taken in a south-north transect east of Svalbard as part of the Nansen Legacy project. Collectively, these biomarkers can be used to reconstruct seasonal spring sea-ice (SpSIC) and the seasonal sea-ice edge. Eight sites at ~78-83°N were sampled by multicorer. All cores contain abundant biomarkers, except the northernmost station. Biomarker-based SpSIC shows a general south-north increase, mimicking observational sea-ice concentration satellite-based means (1988-2017). The HBI T<sub>25</sub> index suggests ice edge phytoplankton blooms at southern stations, agreeing with the general pattern of increased phytoplankton HBIs previously reported from the eastern Barents Sea. As a next step, these new biomarker findings will be used to reconstruct longer-term (Holocene) variability in sea-ice in this region. </p>

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