RECENT CHANGES IN JULY-OCTOBER SEA ICE IN THE BEAUFORT SEA: 1997-2012

Mike Brady

Univers i ty o f Water loo

INTRODUCTION

• The Beaufort Sea; a key area of interestRecord minimum sea ice extents in recent years

Decreases in sea ice thickness and concentration increase the ice cover’s vulnerability to external forcing

Freshwater retention increasing due to a strengthening Beaufort Gyre (Giles et al., 2012)

Beaufort GyreTransport mechanism unique to Beaufort Sea

Predominantly anti-cyclonic

INTRODUCTION

Figure 1 from Lukovich & Barber (2012)

INTRODUCTION

• ObjectivesProduce a time series of sea ice flux between the Beaufort Sea and the Canada Basin

Generate a monthly climatology of sea ice motion for the Beaufort Sea

Beaufort SeaCanadian Arctic Archipelago to Barrow, Alaska

Extents of CIS WA regional ice charts

STUDY AREA

DATA AND METHODS

• RADARSAT-1 & RADARSAT-2 ScanSAR Wide (500km) imagery100m pixel size resampled to 200m

~29,000 usable swaths (11,441 for July-Oct)

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec1997 114 81 104 90 119 125 189 177 52 14 171 1201998 86 124 137 129 128 141 164 171 144 151 149 1371999 132 125 144 147 173 185 189 188 172 187 176 1852000 187 164 139 168 164 168 188 193 204 155 143 1742001 162 166 184 176 194 183 246 239 211 224 218 2082002 189 174 172 159 177 180 194 243 223 192 166 472003 215 171 199 165 182 218 256 257 259 256 234 2302004 234 235 246 202 212 165 234 251 238 256 228 2322005 234 186 198 176 186 157 182 221 217 200 233 2422006 222 180 234 212 194 180 208 214 232 255 234 2392007 292 246 293 292 282 278 297 294 295 273 214 1882008 142 119 129 160 11 1 10 144 83 26 58 352009 23 20 25 26 43 34 75 99 102 75 34 322010 10 12 5 46 48 39 97 181 149 110 35 312011 27 19 20 46 45 32 81 155 170 160 73 452012 73 58 63 71 54 60 78 142 152 147 101 77

3,244

29,467 Total Images

918 588 763 873

1,076

Monthly Summary of RADARSAT1+2 ScanSAR swaths used for CIS-ASITS processing (Imagery downloaded from ASF-URSA/NRCan NEODF)Year Total

1,356 1,661 2,003 2,047 2,411 2,116 2,642 2,733 2,432 2,604

CIS-ASITSIdentify and track suitable ice parcels in sequential SAR image pairs

Estimate rotational and translational components of ice motion through phase correlation approach (Komarov & Barber, 2012)

Previously applied in related works (Howell et al., 2013; Wohelleben et al., 2013)

DATA AND METHODS

Flux Estimation“North Beaufort” Gate

• 756 km

Inflow and outflow estimated from CIS-ASITS outputs coupled with CIS ice concentrations

DATA AND METHODS

LIMITATIONS OF METHODS

• CIS-ASITS has difficulty resolving suitable ice floes in summer months due to surface melt

• Gate length introduces issues with multi-crossings and possible exaggerated/misrepresented motion estimates

• Decreased availability of imagery in RADARSAT-2 portion of study (mid-2008 to 2012) may misrepresent motion and affect flux estimates

EXAMPLES OF MULTI-CROSSINGS

pair_19980929163642_19980930160719 pair_20031029160133_20031030015905

RESULTSNorth Beaufort Monthly Ice Flux 1997-2012

Month

Jul Aug Sep Oct

Ice

Are

a F

lux

(x10

4 k

m2)

-15

-10

-5

0

5

10

15

20

25

MeanMin/Max

RESULTSNorth Beaufort Monthly Ice Flux & MYI Concentrations 1997-2012

Year (July-Oct)

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

Ice

Are

a F

lux

(x

104 k

m2)

-10

0

10

20

MY

I Co

nce

ntratio

n (ten

ths

)

0.0

0.2

0.4

0.6

0.8

1.0

RESULTSNorth Beaufort Net Flux (Jul-Oct)

Year

1997 1999 2001 2003 2005 2007 2009 2011

Ice

Are

a F

lux

(x1

04 k

m2)

-20

-10

0

10

20

30

40

All Ice TypesMYI-Only

RESULTS

NEXT STEPS

• Validate flux estimates with ground data (IABP buoy drift tracks)

• Conduct more robust comparisons with climate variables (NCEP/NCAR Sea Level Pressure/Vector Wind/Air Temperature)

• Finish generating monthly composites of ice motion vectors from CIS-ASITS outputs

THANK YOU• References

Giles, K. A., Laxon, S. W., Ridout, A. L., Wingham, D. J., & Bacon, S. (2012). Western Arctic Ocean freshwater storage increased by wind-driven spin-up of the Beaufort Gyre. Nature Geoscience, 5(3), 194–197. doi:10.1038/ngeo1379

Howell, S. E. L., Wohlleben, T., Dabboor, M., Derksen, C., Komarov, A., & Pizzolato, L. (2013). Recent changes in the exchange of sea ice between the Arctic Ocean and the Canadian Arctic Archipelago. Journal of Geophysical Research: Oceans, 118(7), 3595–3607. doi:10.1002/jgrc.20265

Komarov, A., & Barber, D. (2012). Detection of sea ice motion from co- and cross-polarization RADARSAT-2 images. In 2012 IEEE International Geoscience and Remote Sensing Symposium (Vol. 7, pp. 3277–3280). IEEE. doi:10.1109/IGARSS.2012.6350604

Lukovich, J. V., & Barber, D. G. (2006). Atmospheric controls on sea ice motion in the southern Beaufort Sea. Journal of Geophysical Research , 111(D18), 1–12. doi:10.1029/2005JD006408

Wohlleben, T., Howell, S. E. L., Agnew, T., & Komarov, A. (2013). Sea-Ice Motion and Flux within the Prince Gustaf Adolf Sea, Queen Elizabeth Islands, Canada during 2010. Atmosphere-Ocean, 51(1), 1–17. doi:10.1080/07055900.2012.750232