Ice Area (×104km2)

Ice AreaWind Speed

Shinsuke IWASAKIPort and Coast Research Team
Civil Engineering Research Institute for Cold Region (CERI)
Public Works Research Institute (PWRI)

Julian Day (10/01~)

5 m/s

For more information ↓Increase in the wave power caused by decreasing sea ice over theSea of Okhotsk in winterIwasaki (2023; Scientific Reports)
Engineering Top 100 of 2023
Earth, Environment and Ecology Top 100 of 2023
国立研究開発法人 土木研究所

寒地土木研究所

9th GEWEX-OSC 2024 SAPPORO (2024/07/11)

Color： Ice Concentration
Vectors： Wind Speed(%)

1Wind Speed (m/s)

Increase in the wave power due to the reduction ofsea ice over the Sea of Okhotsk

Introduction
⾵windの海氷 Wave development

波浪減衰効果がある。
波が発達
Sea ice has a wave
attenuation effect.

⾵wind

10年
Inter-annual change of maximum sea ice extent (104km2 )⾵- 3.5%/decade

最⼤海氷域⾯積の経年変化 (104km2 )→10年で3.5%減少

From JMA’s HP

Increasedwaves coming to the coastal areas, and with them,
波が抑制

気象

・Increased high wave damage
・Acceleration of coastal erosion
・Decreased coastal structure stability

Concerned about the increase in disaster cases.
沿岸域に来襲する→Wave suppression

波が抑制

国立研究開発法人 土木研究所

寒地土木研究所や、それに付随す・Are waves in the Sea of Okhotsk
increasing?
If so, what are the causes ?
・⾼波被害の増加
気象庁のHPより・海岸侵⾷の促進
2

Method (Wave Model) Wave model (WW3)

Input data

Sea Ice

Reference

NOAA OISST

Kobayashi et al., (2015), Reynoldset al., (2007), Huang et al., (2021)

ERA5

ERA5

Hersbach et al., (2020)

MERRA2

MERRA2

Gelaro et al., (2017)

WindJRA55

Input

Model

WAVEWATCH III (Ver. 6.07)

Spatial reso.

Domain1(0.25 ), Domain2 (0.08 )Frequency space

0.035-1.1 Hz (30 increments)

Directional reso.

10

Input・Dissipation term

ST6Ice source term

IC4M2 (Meylan et al., 2014)

Coastline・Bottom Topo.

GEBCO2020

Computation period : 1981/09~2021/08 (40 years)

Model Experiments
・CTL runs (３case)・Clim-ICE runs（３case）
Clim-ICE（Climatological sea ice values used)→ Wave variation due to surface wind only
CTL−Clim-ICE → Wave variation due to sea ice only
国立研究開発法人 土木研究所

寒地土木研究所

3

Trend of Wave Power (Pw) over the Sea of Okhotsk

国立研究開発法人 土木研究所

寒地土木研究所

4Trend of Wave Power (Pw) over the Sea of Okhotsk
Linear trend of wave power (Dec—Feb.)
Trend [kW m-1/decade]Ratio [%/decade]

JRA55

1.31

12.7

ERA5

1.19

15.3

MERRA20.83

12.1

Linear trends of surface wind and ice area (Dec—Feb.)
Wind [ms-1/decade]Ice Area [×104 km2/decade]JRA55, NOAA OI

0.27 (3.21)-1.26 (-3.52)

ERA5

0.17 (2.11)-4.65 (-10.73)

MERRA20.14 (1.73)-2.45 (-6.79)

Values in parentheses indicate the relative trends (%/decade)Increased surface wind ? or Reduced sea ice ?
国立研究開発法人 土木研究所

寒地土木研究所

4Numerical Experiments (CTL and Clim-ICE runs)
CTL runCTL (Increased wind + Reduced ice)

Wave model

Clim-ICE run → (Increased wind only)

Climatological Sea Ice

Wavemodel

CTL run – Clim-ICE run = Reduced Sea Ice Only
国立研究開発法人 土木研究所

寒地土木研究所

5

Contributions of wind and sea ice

国立研究開発法人 土木研究所

寒地⼟⽊研究所・岩﨑慎介
寒地土木研究所

6

Contributions of wind and sea ice

Linear trend of wave power (Dec—Feb.)
Contribution of surface wind

Contribution of sea ice

Clim-ICE [kWm-1/decade]

CTL – Clim-ICE [kWm-1/decade]

JRA55

0.81

0.5ERA50.50.69

MERRA20.360.47

国立研究開発法人 土木研究所

寒地⼟⽊研究所・岩﨑慎介
寒地土木研究所

6

Relationship between surface wind and Sea ice

Wave variation due to sea ice(Inter-annual variability:Dec.-Feb.)

Data number :40
国立研究開発法人 土木研究所

寒地⼟⽊研究所・岩﨑慎介
寒地土木研究所↑ Wave variation due to surface wind7

Modification of winds by sea ice
Pressure adjustment mechanism

Lindzen et al., (1987), Alkama et al., (2020)

Low

High

Low

Highwindwind→

Sea ice reduction → Decrease in sea level pressure (SLP)→ Enhanced horizontal gradient of SLP → Increased surface wind
国立研究開発法人 土木研究所

寒地土木研究所

8Modification of winds by sea ice

国立研究開発法人 土木研究所

寒地⼟⽊研究所・岩﨑慎介
寒地土木研究所

9

・ Wave power (Pw) showed a significantly positivetrend (〜12-15% per decade) during winter (Dec. Feb.).

Ice Area (×104km2)

・ The long–term trends of wave power (Pw) in the Seaof Okhotsk were investigated using the 40-year (fromthe 1980s) simulations.

Ice AreaWind Speed

Julian Day (10/01~)

5 m/s

・ The reduction of sea ice is the most important factor
responsible for the positive Pw trend.
Color： Ice Concentration
Vectors： Wind Speed(%)

国立研究開発法人 土木研究所

寒地土木研究所

10Wind Speed (m/s)

Summary

・ Wave power (Pw) showed a significantly positivetrend (〜12-15% per decade) during winter (Dec. ThankFeb.). you for your attention

Ice Area (×104km2)

・ The long–term trends of wave power (Pw) in the Seaof Okhotsk were investigated using the 40-year (fromthe 1980s) simulations.

Ice AreaWind Speed

Julian Day (10/01~)

5 m/s

・ The reduction of sea ice is the most important factor
responsible for the positive Pw trend.
Color： Ice Concentration
Vectors： Wind Speed(%)

国立研究開発法人 土木研究所

寒地土木研究所

10Wind Speed (m/s)

Summary