Variability of <scp>A</scp>rctic sea‐ice topography and its impact on the atmospheric surface drag

Castellani, Giulia; Lüpkes, Christof; Hendricks, Stefan; Gerdes, Rüdiger

doi:10.1002/2013jc009712

Cited by 72 publications

(121 citation statements)

References 48 publications

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“…the Beaufort Sea or Gulf of St Lawrence) the C DN10 subjective median values are 2.2-3.0 × 10 −3 . More recently, Castellani et al (2014) use airborne-derived laser altimeter data gathered between 1995 and 2011 in conjunction with a sea-ice drag parametrisation scheme to demonstrate the considerable topographic and geographic variability in C DN10 over Arctic pack ice, with values ranging between 1.5 and 3 × 10 −3 , largely corroborating the results of earlier studies.…”

Section: Introductionsupporting

confidence: 77%

Observations of surface momentum exchange over the marginal ice zone and recommendations for its parametrisation

et al. 2016

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Abstract. Comprehensive aircraft observations are used to characterise surface roughness over the Arctic marginal ice zone (MIZ) and consequently make recommendations for the parametrisation of surface momentum exchange in the MIZ. These observations were gathered in the Barents Sea and Fram Strait from two aircraft as part of the Aerosol-Cloud Coupling And Climate Interactions in the Arctic (ACCA-CIA) project. They represent a doubling of the total number of such aircraft observations currently available over the Arctic MIZ. The eddy covariance method is used to derive estimates of the 10 m neutral drag coefficient (C DN10 ) from turbulent wind velocity measurements, and a novel method using albedo and surface temperature is employed to derive ice fraction. Peak surface roughness is found at ice fractions in the range 0.6 to 0.8 (with a mean interquartile range in C DN10 of 1.25 to 2.85 × 10 −3 ). C DN10 as a function of ice fraction is found to be well approximated by the negatively skewed distribution provided by a leading parametrisation scheme (Lüpkes et al., 2012) tailored for sea-ice drag over the MIZ in which the two constituent components of drag -skin and form drag -are separately quantified. Current parametrisation schemes used in the weather and climate models are compared with our results and the majority are found to be physically unjustified and unrepresentative. The Lüpkes et al. (2012) scheme is recommended in a computationally simple form, with adjusted parameter settings. A good agreement holds for subsets of the data from different locations, despite differences in sea-ice conditions. Ice conditions in the Barents Sea, characterised by small, unconsolidated ice floes, are found to be associated with higher C DN10 values -especially at the higher ice fractions -than those of Fram Strait, where typically larger, smoother floes are observed. Consequently, the important influence of sea-ice morphology and floe size on surface roughness is recognised, and improvement in the representation of this in parametrisation schemes is suggested for future study.

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Section: Introductionsupporting

confidence: 77%

Observations of surface momentum exchange over the marginal ice zone and recommendations for its parametrisation

et al. 2016

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“…In this study we employ the elevation threshold approach, which has been used extensively in previous studies (e.g. Wadhams, 1980;Dierking, 1995;Martin, 2007;Tan et al, 2012;Castellani et al, 2014). Typically, a ridge (or surface feature) is detected if it has a height above the local level ice/snow surface greater than a chosen elevation threshold.…”

Section: Sea Ice Topography Characterizationmentioning

confidence: 99%

“…Different elevation thresholds are then used to differentiate different topographic features of the ice cover. Castellani et al (2014), for example, used 20 and 80 cm thresholds to differentiate "big" sails from "small" sails/snow features. Sastrugi heights were measured during the Sever airborne program (Warren et al, 1999, Fig.…”

Section: Sea Ice Topography Characterizationmentioning

confidence: 99%

“…Linear profiling studies calculating atmospheric form drag (e.g. Castellani et al, 2014) simply measure the spacing between unique surface features along the linear profile, assuming that the features are randomly orientated and sufficiently sampled for this assumption to be valid. Mock et al (1972) showed that for randomly oriented ridges, the average ridge frequency, µ, and the average ridge density (the ratio of the total length of ridges per unit area), R D , are related via µ = (2/π )R D .…”

Section: Feature Geometry and The Potential For Additional Feature Chmentioning

confidence: 99%

“…More recently, Doble et al (2011) used coincident autonomous underwater vehicle (AUV) sonar and airborne laser profiling to perform a high-resolution, three-dimensional analysis of sea ice morphology; however this was limited to one region within the Beaufort Sea. Efforts have been made to compile existing data sets of pressure ridge morphology (Strub-Klein and Sudom, 2012) and airborne surface profiling (Castellani et al, 2014), to increase spatial and temporal coverage. Unfortunately, these data remain sparse (they do not provide annual data on a basin scale), and are predominantly based on linear profiling of surface features.…”

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confidence: 99%

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Characterizing Arctic sea ice topography using high-resolution IceBridge data

et al. 2016

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Abstract. We present an analysis of Arctic sea ice topography using high-resolution, three-dimensional surface elevation data from the Airborne Topographic Mapper, flown as part of NASA's Operation IceBridge mission. Surface features in the sea ice cover are detected using a newly developed surface feature picking algorithm. We derive information regarding the height, volume and geometry of surface features from 2009 to 2014 within the Beaufort/Chukchi and Central Arctic regions. The results are delineated by ice type to estimate the topographic variability across first-year and multi-year ice regimes.The results demonstrate that Arctic sea ice topography exhibits significant spatial variability, mainly driven by the increased surface feature height and volume (per unit area) of the multi-year ice that dominates the Central Arctic region. The multi-year ice topography exhibits greater interannual variability compared to the first-year ice regimes, which dominates the total ice topography variability across both regions. The ice topography also shows a clear coastal dependency, with the feature height and volume increasing as a function of proximity to the nearest coastline, especially north of Greenland and the Canadian Archipelago. A strong correlation between ice topography and ice thickness (from the IceBridge sea ice product) is found, using a square-root relationship. The results allude to the importance of ice deformation variability in the total sea ice mass balance, and provide crucial information regarding the tail of the ice thickness distribution across the western Arctic. Future research priorities associated with this new data set are presented and discussed, especially in relation to calculations of atmospheric form drag.

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A stability‐dependent parametrization of transfer coefficients for momentum and heat over polar sea ice to be used in climate models

Lüpkes

Gryanik

2015

JGR Atmospheres

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Key Points:• A stability-dependent parametrization of form drag over sea ice is derived • The effect of floe edges on heat transfer coefficients is parametrized • Maximum surface drag depends on both sea ice concentration and stability Abstract The interaction between sea ice and atmosphere depends strongly on the near-surface transfer coefficients for momentum and heat. A parametrization of these coefficients is developed on the basis of an existing parametrization of drag coefficients for neutral stratification that accounts for form drag caused by the edges of ice floes and melt ponds. This scheme is extended to better account for the dependence of surface wind on limiting cases of high and low ice concentration and to include near-surface stability effects over open water and ice on form drag. The stability correction is formulated on the basis of stability functions from Monin-Obukhov similarity theory and also using the Louis concept with stability functions depending on the bulk Richardson numbers. Furthermore, a parametrization is proposed that includes the effect of edge-related turbulence also on heat transfer coefficients. The parametrizations are available in different levels of complexity. The lowest level only needs sea ice concentration and surface temperature as input, while the more complex level needs additional sea ice characteristics. An important property of our parametrization is that form drag caused by ice edges depends on the stability over both ice and water which is in contrast to the skin drag over ice. Results of the parametrization show that stability has a large impact on form drag and, thereby, determines the value of sea ice concentration for which the transfer coefficients reach their maxima. Depending on the stratification, these maxima can occur anywhere between ice concentrations of 20 and 80%.

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Variability of Arctic sea‐ice topography and its impact on the atmospheric surface drag

Cited by 72 publications

References 48 publications

Observations of surface momentum exchange over the marginal ice zone and recommendations for its parametrisation

Observations of surface momentum exchange over the marginal ice zone and recommendations for its parametrisation

Characterizing Arctic sea ice topography using high-resolution IceBridge data

A stability‐dependent parametrization of transfer coefficients for momentum and heat over polar sea ice to be used in climate models

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