Edge of the Arctic multiyear ice @ 83.2N, 62.0E on August 14, 2007

Some thoughts Some thoughts on sea ice retreat in on sea ice retreat in 20072007

Takashi Kikuchi (& Jun Inoue)Takashi Kikuchi (& Jun Inoue)Institute of Observational Research for Global ChangeInstitute of Observational Research for Global ChangeJapan Agency for Marine Earth Science and TechnologyJapan Agency for Marine Earth Science and Technology

IABP 18 annual meetingAt CLS on June 16-18 2008

Photo during the USCGC Healy Trans-Arctic cruisebetween Aug.5 and Sept. 30, 2005

Sea Ice drift speed Sea Ice drift speed and Ocean-to-ice and Ocean-to-ice

heat fluxheat flux

Takashi Kikuchi Takashi Kikuchi Institute of Observational Research for Global Change/Institute of Observational Research for Global Change/

Japan Agency for Marine-earth Science and TechnologyJapan Agency for Marine-earth Science and Technology

(IORGC/JAMSTEC)(IORGC/JAMSTEC)

Photo during the USCGC Healy Trans-Arctic cruisebetween Aug.5 and Sept. 30, 2005

Ocean-to-Ice Heat Flux estimation Ocean-to-Ice Heat Flux estimation (Kikuchi et al., in preparation)(Kikuchi et al., in preparation)

Ocean-to-Ice Heat Flux estimated by using ice-drifting buoy data(e.g., McPhee et al., 2003)

ρ: water density, Cp: specific heat of seawater,

CH: bulk heat transfer coefficient,

u*0: internal friction velocity,

δT: temperature above the freezing point

κ: von Karman's constant (0.4), V: ice velocity relative to the surface geostrophic flowf: Coriolis parameter, z0: hydrographic roughness of the ice undersurface,

A & B; constants for neutral static stability (with values 2.12 and 1.91, respectively).

TuCCH Hpf 0*

iBAfz

u

u

V

0

0*

0*

log

Polar Ocean Profiling System (POPS)

J-CAD 6/2003

JAMSTEC Compact Arctic Drifter (J-CAD)

POPS / 2006

Photo during the USCGC Healy Trans-Arctic cruisebetween Aug.5 and Sept. 30, 2005

Drifting tracks of JAMSTEC buoys deployed near the North Pole since 2000

NB

NGR

AB

LRMB

7 days moving-averaged Ocean-to-Ice Heat Flux detected by J-CAD & POPS data

Apr. May Jun. July Aug. Sept. Oct. Nov. Dec.

Ocean-to-Ice Heat Flux estimation Ocean-to-Ice Heat Flux estimation (Kikuchi et al., in preparation)(Kikuchi et al., in preparation)

Ocean-to-Ice Heat Flux estimation

Interannual variability in ocean-to-ice heat flux prior to NPEO period using 1979-2005 IABP sea ice motion data (upper panel).

Lower panel:Interannual variability in ocean-to-ice heat flux in the Transpolar Drift region estimated by Krishfield and Perovich [2005]

Sea ice drift speed in JJ is the most important indicators in determining the annual average ocean-to-ice heat flux.

Increasing trend

Decreasing trend

Courtesy of E. Hudson and C. Haas

Trend of Ocean-to-Ice Heat Flux

Perovich et al., 2008GRL. Fig.1 (Lower)

Conclusion

Edge of the Arctic multiyear ice @ 83.2N, 62.0E on August 14, 2007

Apr. May Jun. July Aug. Sept. Oct. Nov. Dec.Apr. May Jun. July Aug. Sept. Oct. Nov. Dec.

1.42 W m1.42 W m-2-2

15cm15cm

1.39 W m1.39 W m-2-2

15cm15cm

1.52 W m1.52 W m-2-2

16cm16cm

1.92 W m1.92 W m-2-2

21cm21cm

2.89 W m2.89 W m-2-2

31cm31cm

3.10 W m3.10 W m-2-2

35cm35cm

1) Using ice-drifting buoy data, we 1) Using ice-drifting buoy data, we examined ocean-to-ice heat flux (examined ocean-to-ice heat flux (HHff) in ) in the Transpolar Drift since 2000. The the Transpolar Drift since 2000. The yearly averaged yearly averaged HHff was greater in 2000 was greater in 2000 and 2002 than in 2004-2006. and 2002 than in 2004-2006. 2) Sea ice drift speed in June and July is 2) Sea ice drift speed in June and July is the most important factor in determining the most important factor in determining total heat input from the atmosphere to total heat input from the atmosphere to beneath sea ice during melting season. beneath sea ice during melting season.

3) We suggest that 3) We suggest that HHff displayed an displayed an increasing trend before the early 1990s, increasing trend before the early 1990s, but weakly decreasing trend after the but weakly decreasing trend after the mid 1990s until mid 1990s until at least the mid-2000s. at least the mid-2000s.

However, ……….

Ice concentration of the Arctic Ocean on September 16, 2007. Note that the extent of Arctic summer sea ice in 2007 reached a record minimum. Picture was downloaded from NASA Earth Observatory web site http://earthobservatory.nasa.gov/

As everyone (might) knows, extent of Arctic summer sea ice in 2007 reached a record

minimum.

Minimum ice extent in September 1979~2000: 7.0 x 106 km2

2005: 5.3 x 106 km2

2007: 4.1 x 106 km2September sea ice extent [Updated Inoue and Kikuchi (2007,JMSJ)]

Minimum ice extent in September 1979~2000: 7.0 x 106 km2

2005: 5.3 x 106 km2

2007: 4.1 x 106 km2September sea ice extent [Updated Inoue and Kikuchi (2007,JMSJ)]

Cf. Japan Is. : 0.38 x 106 km2

* Note that ice reduction in 2007 from 2005 ice extent was about 2.8 times as large as the area of Japan Islands.

What is the reason of

sea ice reduction in 2007?

Ice concentration of the Arctic Ocean on September 16, 2007. Note that the extent of Arctic summer sea ice in 2007 reached a record minimum. Picture was downloaded from NASA Earth Observatory web site http://earthobservatory.nasa.gov/

As everyone (might) knows, extent of Arctic summer sea ice in 2007 reached a record

minimum.

1. Thermodynamical reason Sea ice formation and melting Radiation, wind, cloud, snow, ice thickness, ocean heat content

e.g., Shimada et al., 2006 GRL Catastrophic reduction of Arctic Sea Ice (Warming of the western

Arctic Ocean)

Perovich et al., 2008 GRL Sunlight, water, and ice: Extreme Arctic Sea ice melt during the

summer of 2007

Inoue et al., 2008 JGRTransmittance of SW radiation through sea ice and melt pond

2. Dynamical reason Sea ice motion Wind and/or ocean current

e.g., Inoue and Kikuchi, 2007 JMSJOutflows of summertime Arctic sea ice

Transmittance of SW radiation through sea ice and melt pondInoue, Kikuchi and Perovich [JGR 2008]

Using XCTD and sea ice monitoring data during the Healy trans-Arctic cruise in 2005, we examined a relationship between sea ice condition (concentration, pond fraction) and ocean mixed-layer temperature and quantified transmittance of SW radiation through sea ice and melt pond.

(Left) Panorama view of sea ice condition on August 14, 2005 at 78.2N, 153.5W. Inoue et al. [2008]

Schematic of Inoue et al. [2008]

20074.1 million km2

IPCC model

Ice extent In September

For reducing uncertainness of the model prediction of the Arctic ice condition…..

Edge of the Arctic multiyear ice @ 83.2N, 62.0E on August 14, 2007

Outflow of Summertime Arctic Sea Ice Observed by Ice Drifting Buoys and its Linkage with Ice Reduction and

Atmospheric Circulation Patterns Inoue and Kikuchi [2007, JMSJ]

J-CAD 6/2003 POPS / 2006

HH

LL

Color contours: Drifting trajectories for each year (thick line: June-September)Black contour: mean SLP from June to September 2005Shading: anomalies of sea-ice in September 2005 relative to previous 5-year average

In the summer of 2005, our drifting buoy went out from the Arctic Ocean with the fastest speed in the 2000s

Beaufort high and Siberian lowSiberian low pressure systems were dominant in 2005 summer. These systems made strong pressure gradient over the Transpolar Drift region and accelerated sea ice driftaccelerated sea ice drift toward the Fram Strait.

Edge of the Arctic multiyear ice @ 83.2N, 62.0E on August 14, 2007

Summer SLP (JJAS) regressed on sea-ice extent in September

Similar pattern emerged in

summer 2005

Summer SLP change regressed on raw Arctic sea-ice extent in Sept. Strong SLP gradient between Canadian Basin & Siberia

Ice Extent of the Arctic Ocean in September

Summer SLP gradient over Transpolar Drift

Sea ice decrease in the Arctic Ocean

　↓SLP decreasing trend over the Siberian shelf of the Arctic Ocean　↓Produce strong pressure gradient over Transpolar Drift

　↓Enhance ice export from the Arctic Ocean Enhance ice export from the Arctic Ocean

2005: SLP gradient had a maximum record !!

How was 2007 ?How was 2007 ?

LL

LL

HHIce Extent of the Arctic Ocean in September

Summer SLP gradient over Transpolar Drift

Maximum SLP gradient AGAIN !!

7

Sea ice decrease in the Arctic Ocean Sea ice decrease in the Arctic Ocean

　↓　↓SLP decreasing trend over the SLP decreasing trend over the Siberian shelf of the Arctic OceanSiberian shelf of the Arctic Ocean　↓　↓Produce strong pressure gradient Produce strong pressure gradient over Transpolar Drift over Transpolar Drift

　↓　↓Enhance ice export from the Arctic Ocean Enhance ice export from the Arctic Ocean

LL

LL

HH

Strong SLP gradient accelerated Strong SLP gradient accelerated Warm air & water advection !!Warm air & water advection !!

Ice concentration of the Arctic Ocean on September 16, 2007. Note that the extent of Arctic summer sea ice in 2007 reached a record minimum. Picture was downloaded from NASA Earth Observatory web site http://earthobservatory.nasa.gov/

As everyone (might) knows, extent of Arctic summer sea ice in 2007 reached a record

minimum.

Warming of Warming of the Arctic Oceanthe Arctic Ocean

Outflow of sea iceOutflow of sea ice