Wave – Ice Interactions in the Marginal Ice Zone of the Beaufort...
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Wave – Ice Interactions in the Marginal Ice Zone of the Arctic Will Perrie¹, Bash Toulany 1 , Mike Meylan 2 , Yongcun Hu 1 , Mike Casey 1 ¹Bedford Institute of Oceanography, Dartmouth, Canada ²University of Newcastle, Callaghan, Australia
Transcript of Wave – Ice Interactions in the Marginal Ice Zone of the Beaufort...
Wave – Ice Interactions in the Marginal Ice Zone of the Arctic
Will Perrie¹, Bash Toulany1, Mike Meylan2, Yongcun Hu1, Mike Casey1
¹Bedford Institute of Oceanography, Dartmouth, Canada ²University of Newcastle, Callaghan, Australia
Outline
• Motivation…
• Basic model for wave-ice interactions
• Calibration tests
• Simulations and comparisons with field data
• Conclusions
Motivation: Present and future (2035) Arctic…
Regional climate model (25km resolution) driven by HADLEY GCM data, driving NEMO-LIM ice-ocean model… IPCC rcp8.5
Hezel et al. 2014 ClimDyn
Basic wave-ice interactions modelIn the open ocean, waves satisfy the action balance equation
𝜕𝑡𝑁 + 𝑐𝑔 ∙ 𝛻𝑁 = 𝑆𝑜𝑐𝑒𝑎𝑛 + 𝑆𝑖𝑐𝑒
where wave action is 𝑁(𝑘, 𝜃, 𝑥, 𝑡) and in the absence of currents wave
spectral wave energy is 𝐹 𝑘, 𝜃 = 𝜎𝑁(𝑘, 𝜃)
and if no ice we have only the wave physics:
𝑆𝑜𝑐𝑒𝑎𝑛 = 𝑆𝑖𝑛 + 𝑆𝑑𝑠 + 𝑆𝑛𝑙→wind input 𝑆𝑖𝑛, wave dissipation 𝑆𝑑𝑠, nonlinear wave-wave interactions, 𝑆𝑛𝑙→ but if there is ice, then there is a wave-ice term, 𝑆𝑖𝑐𝑒→pro-rate the other terms based on the ice-fraction…
Wave-ice interactions:Attenuation 𝛼 and scattering kernel 𝑆𝑓,
And
o For waves in the direction that were incident in the ’ direction
o where H is wave height is water density
o D( - ’) is the scattering amplitude
o assume scattering is isotropic, in MIZ because of random floes
o ice floe concentration is fi
o ice floe area occupied is Af
o wave group speed = /2k
Calibration tests…
o Ocean is 1000 km x 1500 km with MIZ for the eastern [right side] 1000 km: o Grid spacing is 5kmo Wind is 20 m/s from west to easto Ice concentration is 60%, floe thickness 1.5m, floe length is 20m
Wave growth and decay…
1-d wave spectral energy: 10 km before ice edge
1-d wave spectral energy: 5 km after ice edge
1-d wave spectral energy: 400 km after ice edge
1-d wave spectral energy: 1000 km after ice edge
2-d energy 10km before the MIZ edge5km inside the MIZ edge400km inside the MIZ edge1000km inside the MIZ edge
MBS(2018)BIO Model
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RADARSAT-2
Seastate boundary layer experiment in the emerging Arctic Ocean... 2015
Track (October 2015)
AR
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Wave Heightscale
Ice contours
movie by Erick Rogers
Feb 19 2016 SeaState Meeting, Stennis Space Center 15
More Ice Analysis – from NRLComparison of 4 different ice inputs (SSMI analysis, CICE, etc.)
Waves propagating from water into the MIZ…
Attenuation
Ice output points and SWIFT buoys
BIO ice model WW3-IC2Ice concentration
Log 1
0Ef
4
Meylan(2014)
1-d wave attenuation in the MIZ
MODEL
*Obs*
Summary
1. Methodology for wave-ice scattering and attenuation can work efficiently in WW3
2. BIO and MBS wave-ice models are practical for MIZ ice floes3. Sensitivity depends on (a) floe sizes, (b) concentration (c)
thickness… 4. Issues: (a) high frequency attenuation
(b) flexure in ice floes – varies over the Arctic MIZ, (c) floe breaking(d) floe distributions
