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

AR

CT

I C S E A S T AT

E

20

15

O

FF

IC

E

OF N A V A L R

ES

EA

RC

H

RADARSAT-2

Seastate boundary layer experiment in the emerging Arctic Ocean... 2015

Track (October 2015)

AR

CT

I C S E A S T AT

E

20

15

O

FF

IC

E

OF N A V A L R

ES

EA

RC

H

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