On the Definition of Marginal Ice Zone Width

Strong, Courtenay; Foster, D.G.; Cherkaev, Elena; Eisenman, Ian; Golden, Kenneth M.

doi:10.1175/jtech-d-16-0171.1

Cited by 34 publications

(28 citation statements)

References 36 publications

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“…This correction assumes a horizontally strati-fied Arctic atmosphere with an effective temperature to replace the vertical temperature profile and a diffusely reflecting surface viewed under a 50 • incidence angle (Svendsen et al, 1987). The ice concentration then becomes a function of the polarization difference and the atmospheric correction term, which is in general also a function of ice concentration (Svendsen, 1983;Svendsen et al, 1987). Atmospheric influence is assumed to be a smooth function of ice concentration, and a third-order polynomial for ice concentration is solved as a function of polarization difference.…”

Section: Observational Datasetsmentioning

confidence: 99%

Changes of the Arctic marginal ice zone during the satellite era

2020

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Abstract. Many studies have shown a decrease in Arctic sea ice extent. It does not logically follow, however, that the extent of the marginal ice zone (MIZ), here defined as the area of the ocean with ice concentrations from 15 % to 80 %, is also changing. Changes in the MIZ extent has implications for the level of atmospheric and ocean heat and gas exchange in the area of partially ice-covered ocean and for the extent of habitat for organisms that rely on the MIZ, from primary producers like sea ice algae to seals and birds. Here, we present, for the first time, an analysis of satellite observations of pan-Arctic averaged MIZ extent. We find no trend in the MIZ extent over the last 40 years from observations. Our results indicate that the constancy of the MIZ extent is the result of an observed increase in width of the MIZ being compensated for by a decrease in the perimeter of the MIZ as it moves further north. We present simulations from a coupled sea ice–ocean mixed layer model using a prognostic floe size distribution, which we find is consistent with, but poorly constrained by, existing satellite observations of pan-Arctic MIZ extent. We provide seasonal upper and lower bounds on MIZ extent based on the four satellite-derived sea ice concentration datasets used. We find a large and significant increase (>50 %) in the August and September MIZ fraction (MIZ extent divided by sea ice extent) for the Bootstrap and OSI-450 observational datasets, which can be attributed to the reduction in total sea ice extent. Given the results of this study, we suggest that references to “rapid changes” in the MIZ should remain cautious and provide a specific and clear definition of both the MIZ itself and also the property of the MIZ that is changing.

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Section: Observational Datasetsmentioning

confidence: 99%

Changes of the Arctic marginal ice zone during the satellite era

2020

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“…The two comparisons with the smallest separation distances have the best agreement (circled in blue). DOI: https://doi.org/10.1525/ elementa.305.f13 (Thomson et al, 2016), which affects the FSD near the ice edge, and the marginal ice zone is becoming wider in summer (Strong and Rigor, 2013;Strong et al, 2017). As with PJ14, the time series of FSD from TerraSAR-X images (Hwang et al, 2017a) offers a Lagrangian view of the ice cover as the satellite follows clusters of buoys on the drifting sea ice.…”

Section: Seasonal Cycle Of Power-law Exponentmentioning

confidence: 99%

Seasonal evolution of the sea-ice floe size distribution in the Beaufort and Chukchi seas

Stern

Schweiger

Stark

et al. 2018

Elementa: Science of the Anthropocene

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The size distribution of ice floes in the polar seas affects the dynamics and thermodynamics of the ice cover, and ice-ocean models are beginning to include the floe size distribution (FSD) in their simulations. The FSD has previously been reported to follow a power law of the form x−α, where x is the floe size and –α characterizes how steeply the number of floes decreases as x increases. Different studies have found different values of α and different ranges of x over which the power law applies. We found that a power law describes the FSD in the Beaufort and Chukchi seas reasonably well over floe sizes from 2 to 30 km, based on 187 visible-band satellite images (resolution 250 m) acquired during spring through fall of 2013 and 2014. The mean power-law exponent goes through a seasonal cycle in which α increases in spring, peaks in July or August, and decreases in fall. June is the transition month from spring FSD to summer FSD. This cycle is consistent with the processes of floe break-up in spring followed by preferential melting of smaller floes in summer and the return of larger floes after fall freeze-up. We also analyzed 12 high-resolution satellite images acquired near the low-resolution images in space and time. We found that the FSDs from the high-resolution images follow power laws over floe sizes from 10 m to 3 km. While the power-law exponents of the corresponding high- and low-resolution images do not always match in a strict statistical sense, they suggest the plausibility that the FSD follows a single power law over a wide range of floe sizes. This study covers a larger spatial and temporal sampling space and is based on more satellite images than previous studies. Results have been used for model calibration and validation.

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“…Figure shows significant wave heights simulated by Wavewatch in the FSDv2‐WAVE simulation. The 2000–2014 average spatial fields (Figures a, b, d, and e) show waves penetrating into the ice cover, some to large distances but entirely contained within the 80% sea ice concentration contour, sometimes used to define the marginal ice zone (e.g., Strong et al, ). Probability distributions of all monthly mean significant wave heights in sea ice of concentrations greater than 15% reveal larger wave heights in the Antarctic than the Arctic, reducing as a function of concentration.…”

Section: Resultsmentioning

confidence: 99%

Advances in Modeling Interactions Between Sea Ice and Ocean Surface Waves

Roach

Bitz

Horvat

et al. 2019

J Adv Model Earth Syst

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Recent field programs have highlighted the importance of the composite nature of the sea ice mosaic to the climate system. Accordingly, we previously developed a process-based prognostic model that captures key characteristics of the sea ice floe size distribution and its evolution subject to melting, freezing, new ice formation, welding, and fracture by ocean surface waves. Here we build upon this earlier work, demonstrating a new coupling between the sea ice model and ocean surface waves and a new physically based parameterization for new ice formation in open water. The experiments presented here are the first to include two-way interactions between prognostically evolving waves and sea ice on a global domain. The simulated area-average floe perimeter has a similar magnitude to existing observations in the Arctic and exhibits plausible spatial variability. During the melt season, wave fracture is the dominant FSD process driving changes in floe perimeter per unit sea ice area-the quantity that determines the concentration change due to lateral melt-highlighting the importance of wave-ice interactions for marginal ice zone thermodynamics. We additionally interpret the results to target spatial scales and processes for which floe size observations can most effectively improve model fidelity. Plain Language SummaryIn the outer margins of polar sea ice cover, complex interactions occur between sea ice and ocean surface waves. Waves travel through sea ice with properties of in-ice waves dependent on the size of sea ice floes, which are discrete pieces of sea ice. Sea ice may be fractured by waves, and waves determine the type of sea ice formation that occurs. This study presents advances in numerical modeling of these processes, including communication between a sea ice model and a wave model. We investigate how different physical processes determine the perimeter of sea ice floes exposed to the ocean. This in turn determines the amount of melt that occurs at the edge of sea ice floes.

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On the Definition of Marginal Ice Zone Width

Cited by 34 publications

References 36 publications

Changes of the Arctic marginal ice zone during the satellite era

Changes of the Arctic marginal ice zone during the satellite era

Seasonal evolution of the sea-ice floe size distribution in the Beaufort and Chukchi seas

Advances in Modeling Interactions Between Sea Ice and Ocean Surface Waves

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