Ocean wave energy regimes of the circum-polar coastal zoneOcean wave energy regimes of the circum-polar coastal zone

David E. Atkinson

International Arctic Research Center / Atmospheric Sciences DepartmentUniversity of Alaska Fairbanks

David E. Atkinson

International Arctic Research Center / Atmospheric Sciences DepartmentUniversity of Alaska Fairbanks

David E. AtkinsonIARC/Atm. Sci., University of Alaska FairbanksAGU San Fransisco: December 13, 2004

ObjectiveObjective

Provide wave energy climatologies for the Arctic Coastal Dynamics Project Provide wave energy climatologies for the Arctic Coastal Dynamics Project

Photos by Julie Baltar , story in the Nome NuggetShishmaref, AK

Shishmaref, AK bluff retreatShishmaref, AK bluff retreat

David E. AtkinsonIARC/Atm. Sci., University of Alaska Fairbanks

Impacts – Alaska - communitiesImpacts – Alaska - communities

AGU San Fransisco: December 13, 2004

Photos taken 2 hours apartPhotos taken 2 hours apart

Figure given to me by Tohru Saito, IARCFigure given to me by Tohru Saito, IARCImpacts – Alaska - communitiesImpacts – Alaska - communities

MotivationMotivation

> Wave energy principle forcing agent

> Much of the circum-polar coastal zone susceptible to erosion

> Problem is not easy

- shallow zones

- sea ice

* ice on/off dates controls wave access

* position of ice offshore controls fetch

(presence of floating ice also modifies wave energy)

> Coastal process models require wave energy input (I.e., and not wind)

> Engineering issues

> Wave energy principle forcing agent

> Much of the circum-polar coastal zone susceptible to erosion

> Problem is not easy

- shallow zones

- sea ice

* ice on/off dates controls wave access

* position of ice offshore controls fetch

(presence of floating ice also modifies wave energy)

> Coastal process models require wave energy input (I.e., and not wind)

> Engineering issues

David E. AtkinsonIARC/Atm. Sci., University of Alaska FairbanksAGU San Fransisco: December 13, 2004

Desire: develop a system that will translate winds into wave energy

> ERA is available, but

- custom development will allow tailoring

(e.g. force with winds from HIRHAM, upcoming arctic

reanalysis, even AOGCM predicted fields.)

> Generate climatological wave fields

- monthly totals

- annual totals

- period means and trends (1979-2003)

Provide to coastal dymanics researchers, but

can also assess contribution of ice

Desire: develop a system that will translate winds into wave energy

> ERA is available, but

- custom development will allow tailoring

(e.g. force with winds from HIRHAM, upcoming arctic

reanalysis, even AOGCM predicted fields.)

> Generate climatological wave fields

- monthly totals

- annual totals

- period means and trends (1979-2003)

Provide to coastal dymanics researchers, but

can also assess contribution of ice

Scope and ApproachScope and Approach

David E. AtkinsonIARC/Atm. Sci., University of Alaska FairbanksAGU San Fransisco: December 13, 2004

Wave energy calculation

- 1st order linear (Airy) approximation

> Coastal Engineering Manual and Technical

Reference for the Automated Coastal Engineering System

(USArmy Corps of Engineers)

> suitable for most applications

Full complexity of the 3-D fluid structure can not currently be described

in its entirety

Wave energy calculation

- 1st order linear (Airy) approximation

> Coastal Engineering Manual and Technical

Reference for the Automated Coastal Engineering System

(USArmy Corps of Engineers)

> suitable for most applications

Full complexity of the 3-D fluid structure can not currently be described

in its entirety

Scope and ApproachScope and Approach

David E. AtkinsonIARC/Atm. Sci., University of Alaska FairbanksAGU San Fransisco: December 13, 2004

Wind forcing:

- NCEP/NCAR reanalysis, 925 mb to overcome speed problems

- direction limited to 180° (I.e. water side)

Direct forcing approach, not distribution based

Wind forcing:

- NCEP/NCAR reanalysis, 925 mb to overcome speed problems

- direction limited to 180° (I.e. water side)

Direct forcing approach, not distribution based

Scope and ApproachScope and Approach

David E. AtkinsonIARC/Atm. Sci., University of Alaska FairbanksAGU San Fransisco: December 13, 2004

Scope and ApproachScope and Approach

Depth

- simply specified at 10m

- represents generic shelf zone

Sea ice

- NSIDC extent plots used

- coastal region divided into 12 sectors by longitude

- based on ice plots, sectors assigned a binary ice/no ice class

- turned energy on/off for that month

Depth

- simply specified at 10m

- represents generic shelf zone

Sea ice

- NSIDC extent plots used

- coastal region divided into 12 sectors by longitude

- based on ice plots, sectors assigned a binary ice/no ice class

- turned energy on/off for that month

David E. AtkinsonIARC/Atm. Sci., University of Alaska FairbanksAGU San Fransisco: December 13, 2004

ACD zones, weather station locations

Results from Arctic Coastal Dynamics projectResults from Arctic Coastal Dynamics project

David E. AtkinsonIARC/Atm. Sci., University of Alaska FairbanksAGU San Fransisco: December 13, 2004

1

23

5678

9

10

11

12

4

No depth variation

Winds do not catch all events (spatial resolution)

Ice sector approximation

Ice content (binary approach) coarse

Spatial resoution coarse

Orientation of wind energy wrt coastline crude (180 degree thing)

No depth variation

Winds do not catch all events (spatial resolution)

Ice sector approximation

Ice content (binary approach) coarse

Spatial resoution coarse

Orientation of wind energy wrt coastline crude (180 degree thing)

LimitationsLimitations

David E. AtkinsonIARC/Atm. Sci., University of Alaska FairbanksAGU San Fransisco: December 13, 2004

David E. AtkinsonIARC/Atm. Sci., University of Alaska FairbanksAGU San Fransisco: December 13, 2004

1979 total1979 total

ICE No ICE

David E. AtkinsonIARC/Atm. Sci., University of Alaska FairbanksAGU San Fransisco: December 13, 2004

1998 total1998 total

ICE No ICE

David E. AtkinsonIARC/Atm. Sci., University of Alaska FairbanksAGU San Fransisco: December 13, 2004

1979 – 2003 mean1979 – 2003 mean

ICE No ICE

David E. AtkinsonIARC/Atm. Sci., University of Alaska FairbanksAGU San Fransisco: December 13, 2004

1979 – 2003 trends1979 – 2003 trends

ICE No ICE

For example,For example,

> Increase wind forcing resolution

> Introduce local coastal orientation

> Variable depth

> Introduce variable ice concentrations, drop sector approach

> Comparisons with existing observed/modeled information

(e.g. Ogorodov for Pechora Sea)

> Increase wind forcing resolution

> Introduce local coastal orientation

> Variable depth

> Introduce variable ice concentrations, drop sector approach

> Comparisons with existing observed/modeled information

(e.g. Ogorodov for Pechora Sea)

Next steps/improvementsNext steps/improvements

David E. AtkinsonIARC/Atm. Sci., University of Alaska FairbanksAGU San Fransisco: December 13, 2004

David E. AtkinsonIARC/Atm. Sci., University of Alaska FairbanksAGU San Fransisco: December 13, 2004

> Influence of sea ice apparent even for this coarse approach

> Wave energy trends, not just seasonal totals, influenced by sea ice conditions

> Influence of sea ice apparent even for this coarse approach

> Wave energy trends, not just seasonal totals, influenced by sea ice conditions

ConclusionsConclusions