scholarly journals A generalized stress correction scheme for the Maxwell elasto-brittle rheology: impact on the fracture angles and deformations

2021 ◽  
Vol 15 (12) ◽  
pp. 5623-5638
Author(s):  
Mathieu Plante ◽  
L. Bruno Tremblay
Keyword(s):  
Sea Ice ◽  
Stress Tensor ◽  
Yield Curve ◽  
Yield Criterion ◽  
Elastic Response ◽  
The Arctic ◽  
Critical Stresses ◽  
Correction Scheme ◽  
Added Benefit

Abstract. The Maxwell elasto-brittle (MEB) rheology uses a damage parameterization to represent the brittle fracture of sea ice without involving plastic laws to constrain the sea ice deformations. The conventional MEB damage parameterization is based on a correction of super-critical stresses that binds the simulated stress to the yield criterion but leads to a growth of errors in the stress field. A generalized damage parameterization is developed to reduce this error growth and to investigate the influence of the super-critical stress correction scheme on the simulated sea ice fractures, deformations and orientation of linear kinematic features (LKFs). A decohesive stress tensor is used to correct the super-critical stresses towards different points on the yield curve. The sensitivity of the simulated sea ice fractures and deformations to the decohesive stress tensor is investigated in uniaxial compression experiments. Results show that the decohesive stress tensor influences the growth of residual errors associated with the correction of super-critical stresses, the orientation of the lines of fracture and the short-term deformation associated with the damage, but it does not influence the long-term post-fracture sea ice deformations. We show that when ice fractures, divergence first occurs while the elastic response is dominant, and convergence develops post-fracture in the long term when the viscous response dominates – contrary to laboratory experiments of granular flow and satellite imagery in the Arctic. The post-fracture deformations are shown to be dissociated from the fracture process itself, an important difference with classical viscous plastic (VP) models in which large deformations are governed by associative plastic laws. Using the generalized damage parameterization together with a stress correction path normal to the yield curve reduces the growth of errors sufficiently for the production of longer-term simulations, with the added benefit of bringing the simulated LKF intersection half-angles closer to observations (from 40–50 to 35–45∘, compared to 15–25∘ in observations).

scholarly journals A generalized stress correction scheme for the MEB rheology: impact on the fracture angles and deformations

2021 ◽  
Author(s):  
Mathieu Plante ◽  
L. Bruno Tremblay
Keyword(s):  
Stress Tensor ◽  
Yield Curve ◽  
Elastic Response ◽  
The Arctic ◽  
Critical Stresses ◽  
Fracture Deformation ◽  
Correction Scheme ◽  
Simulated Material ◽  
Residual Errors

Abstract. A generalized damage parameterization is developed for the Maxwell Elasto-Brittle (MEB) rheology that reduces the growth of residual errors associated with the correction of super-critical stresses. In the generalized stress correction, a decohesive stress tensor is used to bring the super-critical stresses back on the yield curve based on any correction path. The sensitivity of the simulated material behaviour to the magnitude of the decohesive stress tensor is investigated in uniaxial compression simulations. Results show that while the decohesive stress tensor influences the short-term fracture deformation and orientation, the long-term post-fracture behaviour remains unchanged. Divergence first occurs when the elastic response is dominant followed by post-fracture shear and convergence when the viscous response dominates – contrary to laboratory experiment of granular flow and satellite imagery in the Arctic. The post-fracture deformations are shown to be dissociated from the fracture process itself, an important difference with classical Viscous Plastic (VP) models. Using the generalized damage parameterization together with a stress correction path normal to the yield curve brings the simulated fracture angles closer to observations (from 40–50° to 35–45°, compared to 20–30° in observations) and reduces the growth of errors sufficiently for the production of longer-term simulations.

The implications of selected processing methods on satellite altimetry derived sea ice thickness state and trends in the seasonal ice zone

2021 ◽  
Author(s):  
Isolde Glissenaar ◽  
Jack Landy ◽  
Alek Petty ◽  
Nathan Kurtz ◽  
Julienne Stroeve
Keyword(s):  
Sea Ice ◽  
Snow Depth ◽  
Satellite Altimetry ◽  
Region Of Interest ◽  
The Arctic ◽  
Ice Thickness ◽  
Sea Ice Thickness ◽  
Baffin Bay ◽  
The Impact

<p>The ice cover of the Arctic Ocean is increasingly becoming dominated by seasonal sea ice. It is important to focus on the processing of altimetry ice thickness data in thinner seasonal ice regions to understand seasonal sea ice behaviour better. This study focusses on Baffin Bay as a region of interest to study seasonal ice behaviour.</p><p>We aim to reconcile the spring sea ice thickness derived from multiple satellite altimetry sensors and sea ice charts in Baffin Bay and produce a robust long-term record (2003-2020) for analysing trends in sea ice thickness. We investigate the impact of choosing different snow depth products (the Warren climatology, a passive microwave snow depth product and modelled snow depth from reanalysis data) and snow redistribution methods (a sigmoidal function and an empirical piecewise function) to retrieve sea ice thickness from satellite altimetry sea ice freeboard data.</p><p>The choice of snow depth product and redistribution method results in an uncertainty envelope around the March mean sea ice thickness in Baffin Bay of 10%. Moreover, the sea ice thickness trend ranges from -15 cm/dec to 20 cm/dec depending on the applied snow depth product and redistribution method. Previous studies have shown a possible long-term asymmetrical trend in sea ice thinning in Baffin Bay. The present study shows that whether a significant long-term asymmetrical trend was found depends on the choice of snow depth product and redistribution method. The satellite altimetry sea ice thickness results with different snow depth products and snow redistribution methods show that different processing techniques can lead to different results and can influence conclusions on total and spatial sea ice thickness trends. Further processing work on the historic radar altimetry record is needed to create reliable sea ice thickness products in the marginal ice zone.</p>

scholarly journals Non-normal flow rules affect fracture angles in sea ice viscous–plastic rheologies

2021 ◽  
Vol 15 (6) ◽  
pp. 2873-2888
Author(s):  
Damien Ringeisen ◽  
L. Bruno Tremblay ◽  
Martin Losch
Keyword(s):  
Sea Ice ◽  
Axial Compression ◽  
Yield Curve ◽  
Axial Loading ◽  
The Arctic ◽  
Flow Rule ◽  
Normal Flow ◽  
Fracture Deformation ◽  
Plastic Potential ◽  
Ice Model

Abstract. The standard viscous–plastic (VP) sea ice model with an elliptical yield curve and a normal flow rule has at least two issues. First, it does not simulate fracture angles below 30∘ in uni-axial compression, in contrast with observations of linear kinematic features (LKFs) in the Arctic Ocean. Second, there is a tight, but unphysical, coupling between the fracture angle, post-fracture deformation, and the shape of the yield curve. This tight coupling was identified as the reason for the overestimation of fracture angles. In this paper, these issues are addressed by removing the normality constraint on the flow rule in the standard VP model. The new rheology is tested in numerical uni-axial loading tests. To this end, an elliptical plastic potential – which defines the post-fracture deformations, or flow rule – is introduced independently of the elliptical yield curve. As a consequence, the post-fracture deformation is decoupled from the mechanical strength properties of the ice. We adapt Roscoe's angle theory, which is based on observations of granular materials, to the context of sea ice modeling. In this framework, the fracture angles depend on both yield curve and plastic potential parameters. This new formulation predicts accurately the results of the numerical experiments with a root-mean-square error below 1.3∘. The new rheology allows for angles of fracture smaller than 30∘ in uni-axial compression. For instance, a plastic potential with an ellipse aspect ratio smaller than 2 (i.e., the default value in the standard viscous–plastic model) can lead to fracture angles as low as 22∘. Implementing an elliptical plastic potential in the standard VP sea ice model requires only small modifications to the standard VP rheology. The momentum equations with the modified rheology, however, are more difficult to solve numerically. The independent plastic potential solves the two issues with VP rheology addressed in this paper: in uni-axial loading experiments, it allows for smaller fracture angles, which fall within the range of satellite observations, and it decouples the angle of fracture and the post-fracture deformation from the shape of the yield curve. The orientation of the post-fracture deformation along the fracture lines (convergence and divergence), however, is still controlled by the shape of the plastic potential and the location of the stress state on the yield curve. A non-elliptical plastic potential would be required to change the orientation of deformation and to match deformation statistics derived from satellite measurements.

scholarly journals Sea ice volume variability and water temperature in the Greenland Sea

2020 ◽  
Vol 14 (2) ◽  
pp. 477-495 ◽  
Author(s):  
Valeria Selyuzhenok ◽  
Igor Bashmachnikov ◽  
Robert Ricker ◽  
Anna Vesman ◽  
Leonid Bobylev
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
Heat Content ◽  
The Arctic ◽  
Fram Strait ◽  
Greenland Sea ◽  
Nordic Seas ◽  
Ice Volume ◽  
Long Term Variations

Abstract. This study explores a link between the long-term variations in the integral sea ice volume (SIV) in the Greenland Sea and oceanic processes. Using the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS, 1979–2016), we show that the increasing sea ice volume flux through Fram Strait goes in parallel with a decrease in SIV in the Greenland Sea. The overall SIV loss in the Greenland Sea is 113 km3 per decade, while the total SIV import through Fram Strait increases by 115 km3 per decade. An analysis of the ocean temperature and the mixed-layer depth (MLD) over the climatic mean area of the winter marginal sea ice zone (MIZ) revealed a doubling of the amount of the upper-ocean heat content available for the sea ice melt from 1993 to 2016. This increase alone can explain the SIV loss in the Greenland Sea over the 24-year study period, even when accounting for the increasing SIV flux from the Arctic. The increase in the oceanic heat content is found to be linked to an increase in temperature of the Atlantic Water along the main currents of the Nordic Seas, following an increase in the oceanic heat flux from the subtropical North Atlantic. We argue that the predominantly positive winter North Atlantic Oscillation (NAO) index during the 4 most recent decades, together with an intensification of the deep convection in the Greenland Sea, is responsible for the intensification of the cyclonic circulation pattern in the Nordic Seas, which results in the observed long-term variations in the SIV.

Further development on sea-ice HBI biomarker proxies.

2020 ◽  
Author(s):  
Maria Luisa Sánchez-Montes ◽  
Nikolai Pedentchouk ◽  
Thomas Mock ◽  
Simon Belt ◽  
Lukas Smik
Keyword(s):  
Sea Ice ◽  
The Arctic ◽  
Global Ocean ◽  
Sea Ice Extent ◽  
Climate Conditions ◽  
Crucial Component ◽  
Lipid Biomarker ◽  
Proxy Measure ◽  
Further Development

<p>Sea ice is a crucial component of the Earth’s climate system, which helps regulate global ocean and atmosphere’s temperature. The alarming decline in sea-ice extent and thickness under modern climate conditions has created the urgency to understand the long-term sea-ice variability and mechanisms of change. In recent years, the highly branched isoprenoid (HBI) lipid biomarker IP<sub>25</sub> has emerged as a powerful proxy measure of past sea ice in the Arctic, and its analysis in a variety of marine sediments has provided the foundation for a large number of palaeo sea ice reconstructions spanning thousands to millions of years before present. To date, IP<sub>25</sub> and related HBI-based studies have focussed largely on reconstructions of sea-ice extent and seasonal dynamics. Here we aim to further develop such sea ice proxies by measuring the changes in distribution and isotopic composition of HBIs in HBI-producing diatoms grown under different controlled laboratory conditions. We present preliminary results from the diatom <em>Haslea ostrearia</em> and outline the next steps of our research in the coming year.</p>

scholarly journals Holocene dynamics in the Bering Strait inflow to the Arctic and the Beaufort Gyre circulation based on sedimentary records from the Chukchi Sea

2017 ◽  
Author(s):  
Masanobu Yamamoto ◽  
Seung-Il Nam ◽  
Leonid Polyak ◽  
Daisuke Kobayashi ◽  
Kenta Suzuki ◽  
...  
Keyword(s):  
Sea Ice ◽  
Chukchi Sea ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Circulation System ◽  
Bering Strait ◽  
The Holocene ◽  
Middle Holocene ◽  
Beaufort Gyre

Abstract. The Beaufort Gyre (BG) and the Bering Strait inflow (BSI) are important elements of the Arctic Ocean circulation system and major controls on the distribution of Arctic sea ice. We report records of the quartz/feldspar and chlorite/illite ratios in three sediment cores from the northern Chukchi Sea providing insights into the long-term dynamics of the BG circulation and the BSI during the Holocene. The quartz/feldspar ratio, a proxy of the BG strength, gradually decreased during the Holocene, suggesting a long-term decline in the BG strength, consistent with orbitally-controlled decrease in summer insolation. We suppose that the BG rotation weakened as a result of increasing stability of sea-ice cover at the margins of the Canada Basin, driven by decreasing insolation. Millennial to multi-centennial variability in the quartz/feldspar ratio (the BG circulation) is consistent with fluctuations in solar irradiance, suggesting that solar activity affected the BG strength on these timescales. The BSI approximated by the chlorite/illite record shows intensified flow from the Bering Sea to the Arctic during the middle Holocene, which is attributed primarily to the effect of an overall weaker Aleutian Low. The middle Holocene intensification of the BSI was associated with decrease in sea ice concentrations and increase in marine production, as indicated by biomarker concentrations, suggesting an influence of the BSI on sea ice distribution and biological production in the Chukchi Sea.

scholarly journals Long-term time series of Arctic tropospheric BrO derived from UV–VIS satellite remote sensing and its relation to first-year sea ice

2020 ◽  
Vol 20 (20) ◽  
pp. 11869-11892
Author(s):  
Ilias Bougoudis ◽  
Anne-Marlene Blechschmidt ◽  
Andreas Richter ◽  
Sora Seo ◽  
John Philip Burrows ◽  
...  
Keyword(s):  
Time Series ◽  
Sea Ice ◽  
Ice Age ◽  
The Arctic ◽  
First Year ◽  
Vertical Column ◽  
Chain Reactions ◽  
Heterogeneous Chain ◽  
Good Agreement

Abstract. Every polar spring, phenomena called bromine explosions occur over sea ice. These bromine explosions comprise photochemical heterogeneous chain reactions that release bromine molecules, Br2, to the troposphere and lead to tropospheric plumes of bromine monoxide, BrO. This autocatalytic mechanism depletes ozone, O3, in the boundary layer and troposphere and thereby changes the oxidizing capacity of the atmosphere. The phenomenon also leads to accelerated deposition of metals (e.g., Hg). In this study, we present a 22-year (1996 to 2017) consolidated and consistent tropospheric BrO dataset north of 70∘ N, derived from four different ultraviolet–visible (UV–VIS) satellite instruments (GOME, SCIAMACHY, GOME-2A and GOME-2B). The retrieval data products from the different sensors are compared during periods of overlap and show good agreement (correlations of 0.82–0.98 between the sensors). From our merged time series of tropospheric BrO vertical column densities (VCDs), we infer changes in the bromine explosions and thus an increase in the extent and magnitude of tropospheric BrO plumes during the period of Arctic warming. We determined an increasing trend of about 1.5 % of the tropospheric BrO VCDs per year during polar springs, while the size of the areas where enhanced tropospheric BrO VCDs can be found has increased about 896 km2 yr−1. We infer from comparisons and correlations with sea ice age data that the reported changes in the extent and magnitude of tropospheric BrO VCDs are moderately related to the increase in first-year ice extent in the Arctic north of 70∘ N, both temporally and spatially, with a correlation coefficient of 0.32. However, the BrO plumes and thus bromine explosions show significant variability, which also depends, apart from sea ice, on meteorological conditions.

scholarly journals A scatterometer record of sea ice extents and backscatter: 1992–2016

2018 ◽  
Author(s):  
Maria Belmonte Rivas ◽  
Ines Otosaka ◽  
Ad Stoffelen ◽  
Anton Verhoef
Keyword(s):  
Sea Ice ◽  
The Arctic ◽  
Ice Thickness ◽  
Climate Data ◽  
Sea Ice Thickness ◽  
Antarctic Sea Ice ◽  
New Evidence ◽  
Climate Data Record ◽  
Higher Sensitivity

Abstract. This paper presents the first long-term climate data record of sea ice extents and backscatter derived from inter-calibrated satellite scatterometer missions (ERS, QuikSCAT and ASCAT) extending from 1992 to present date. This record provides a valuable independent account of the evolution of Arctic and Antarctic sea ice extents, one that is in excellent agreement with the passive microwave records during the fall and winter months but shows higher sensitivity to lower concentration and melting sea ice during the spring and summer months, providing a means to correct for summer melt ponding errors. The scatterometer record also provides a depiction of sea ice backscatter at C and Ku-band, allowing the separation of seasonal and perennial sea ice in the Arctic, and further differentiation between second year (SY) and older multiyear (MY) ice classes, revealing the emergence of SY ice as the dominant perennial ice type after the record sea ice loss in 2007, and bearing new evidence on the loss of multiyear ice in the Arctic over the last 25 years. The relative good agreement between the backscatter-based sea ice (FY, SY and older MY) classes and the ice thickness record from Cryosat suggests its applicability as a reliable proxy in the historical reconstruction of sea ice thickness in the Arctic.

scholarly journals Inter-comparison of snow depth retrievals over Arctic sea ice from radar data acquired by Operation IceBridge

2017 ◽  
Author(s):  
Ron Kwok ◽  
Nathan T. Kurtz ◽  
Ludovic Brucker ◽  
Alvaro Ivanoff ◽  
Thomas Newman ◽  
...  
Keyword(s):  
Sea Ice ◽  
Data Quality ◽  
Snow Depth ◽  
Radar Data ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Arctic Sea ◽  
Retrieval Algorithms ◽  
Snow Thickness

Abstract. Since 2009, the ultra-wideband snow-radar on Operation IceBridge has acquired data in annual campaigns conducted during the Arctic and Antarctic springs. Progressive improvements in radar hardware and data processing methodologies have led to improved data quality for subsequent retrieval of snow depth. Existing retrieval algorithms differ in the way the air-snow and snow-ice interfaces are detected and localized in the radar returns, and in how the system limitations are addressed (e.g., noise, resolution). In 2014, the Snow Thickness On Sea Ice Working Group (STOSIWG) was formed and tasked with investigating how radar data quality affect snow depth retrievals and how retrievals from the various algorithms differ. The goal is to understand the limitations of the estimates and to produce a well-documented, long-term record that can be used for understanding broader changes in the Arctic climate system. Here, we assess five retrieval algorithms by comparisons with field measurements from two ground-based campaigns, including the BRomine Ozone Mercury EXperiment (BROMEX) at Barrow, Alaska and a field program by Environment and Climate Change Canada (ECCC) at Eureka, Nunavut, available climatology and snowfall from ERA-Interim reanalysis. The aim is to examine available algorithms and to use the assessment results to inform the development of future approaches. We present results from these assessments and highlight key considerations for the production of a long-term, calibrated geophysical record of springtime snow thickness over Arctic sea ice.

scholarly journals Intercomparison of snow depth retrievals over Arctic sea ice from radar data acquired by Operation IceBridge

2017 ◽  
Vol 11 (6) ◽  
pp. 2571-2593 ◽  
Author(s):  
Ron Kwok ◽  
Nathan T. Kurtz ◽  
Ludovic Brucker ◽  
Alvaro Ivanoff ◽  
Thomas Newman ◽  
...  
Keyword(s):  
Sea Ice ◽  
Data Quality ◽  
Snow Depth ◽  
Radar Data ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Arctic Sea ◽  
Retrieval Algorithms ◽  
Snow Thickness

Abstract. Since 2009, the ultra-wideband snow radar on Operation IceBridge (OIB; a NASA airborne mission to survey the polar ice covers) has acquired data in annual campaigns conducted during the Arctic and Antarctic springs. Progressive improvements in radar hardware and data processing methodologies have led to improved data quality for subsequent retrieval of snow depth. Existing retrieval algorithms differ in the way the air–snow (a–s) and snow–ice (s–i) interfaces are detected and localized in the radar returns and in how the system limitations are addressed (e.g., noise, resolution). In 2014, the Snow Thickness On Sea Ice Working Group (STOSIWG) was formed and tasked with investigating how radar data quality affects snow depth retrievals and how retrievals from the various algorithms differ. The goal is to understand the limitations of the estimates and to produce a well-documented, long-term record that can be used for understanding broader changes in the Arctic climate system. Here, we assess five retrieval algorithms by comparisons with field measurements from two ground-based campaigns, including the BRomine, Ozone, and Mercury EXperiment (BROMEX) at Barrow, Alaska; a field program by Environment and Climate Change Canada at Eureka, Nunavut; and available climatology and snowfall from ERA-Interim reanalysis. The aim is to examine available algorithms and to use the assessment results to inform the development of future approaches. We present results from these assessments and highlight key considerations for the production of a long-term, calibrated geophysical record of springtime snow thickness over Arctic sea ice.

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