基于卫星图像的北极浮冰大小分布特征分析
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摘要
随着全球气候变暖,海冰厚度逐渐变小,海冰面积逐渐缩小,开阔海域的面积越来越大,北极地区海冰也越来越容易受到海浪的侵袭导致浮冰发生破碎,加速海冰融化。因此在全球气候变暖的环境下,分析浮冰大小分布特征,对于研究北极海区的动量和热量收支有着重要意义,同时有助于改进现有的海冰模型。文中基于3种不同空间分辨率的卫星图像,利用限制增长法分析了2014年夏秋季转化季节波弗特海和楚科奇海的浮冰大小分布特征,所用的卫星图像包括Medea图像,RADARSAT-2图像以及Landsat 8图像,3种图像的空间分辨率分别为1 m,15 m和100 m。不同的空间分辨率为研究浮冰大小总体分布特征提供了一个广泛的数据基础,能够更充分地研究不同尺寸的浮冰大小分布。采用的限制增长法,能够自动识别并提取出浮冰,最终得到浮冰大小分布特征满足幂律分布形式,幂指数的范围在0.8~1.91之间,较大的浮冰对应的幂指数也相应较大,且随着远离海冰边界的距离,幂指数有增大的趋势。处于在夏秋转换季节,部分浮冰开始发生冻结,小尺度浮冰数量逐渐减少。
With intensifying global warming, mankind is witnessing the reduction of sea ice and the increase in open waters. The floe in the Arctic is becoming more susceptible to the effects of great waves and apt to fall apart. Under the process of global warming, it is significant for understanding the balance of the momentum and the heat to study the floe size distributions. The restricted growing method is adopted on three different resolutions of the satellite images to study the floe size distributions during 2014 summer-fall transition in the Chukchi and Beaufort Seas. The satellite images include the Medea, RADARSAT-2 and Landsat8 images with the resolutions of 1 m, 15 m and 100 m, respectively. The range of ?oe sizes with different resolutions provides theoverall distribution across a wide range of ice properties. The restricted method is used to extract the floes automatically to get the floe size distribution following the power-law function distribution with the exponent varying from 0.8 to 1.91. The larger floes correspond the larger exponent which has the tendency of increase with increasing distances from the ice edge location. During the summer-fall transitions, the floes are frozen together to make the smaller floes gradually decrease.
With intensifying global warming, mankind is witnessing the reduction of sea ice and the increase in open waters. The floe in the Arctic is becoming more susceptible to the effects of great waves and apt to fall apart. Under the process of global warming, it is significant for understanding the balance of the momentum and the heat to study the floe size distributions. The restricted growing method is adopted on three different resolutions of the satellite images to study the floe size distributions during 2014 summer-fall transition in the Chukchi and Beaufort Seas. The satellite images include the Medea, RADARSAT-2 and Landsat8 images with the resolutions of 1 m, 15 m and 100 m, respectively. The range of ?oe sizes with different resolutions provides theoverall distribution across a wide range of ice properties. The restricted method is used to extract the floes automatically to get the floe size distribution following the power-law function distribution with the exponent varying from 0.8 to 1.91. The larger floes correspond the larger exponent which has the tendency of increase with increasing distances from the ice edge location. During the summer-fall transitions, the floes are frozen together to make the smaller floes gradually decrease.
引文
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[2]Thomson Jim,Rogers,W Erick.Swell and sea in the emerging Arctic Ocean[J].Geophysical Research Letters,2014,41(9):3136-3140.
[3]Kwok R,Cunningham G F,Wensnahan M,et al.Thinning and volume loss of the Arctic Ocean sea ice cover:2003-2008[J].Journal of Geophysical Research Oceans,2009,114(C7):371-377.
[4]Kohout A L,Williams M J,Dean S M,et al.Storm-induced sea-ice breakup and the implications for ice extent[J].Nature,2014,509(7502):604.
[5]Williams T D,Bennetts L G,Squire V A,et al.Wave-ice interactions in the marginal ice zone.Part 1:Theoretical foundations[J].Ocean Modelling,2013,71(4):81-91.
[6]Squire V A.Of ocean waves and sea-ice revisited[J].Cold Regions Science&Technology,2007,49(2):110-133.
[7]Williams T D,Bennetts L G,Squire V A,et al.Wave-ice interactions in the marginal ice zone.Part 2:Numerical implementation and sensitivity studies along 1D transects of the ocean surface[J].Ocean Modelling,2013,71(4):92-101.
[8]Rothrock D A,Thorndike A S.Measuring the sea ice floe size distribution[J].Journal of Geophysical Research Atmospheres,1984,89(C4):6477-6486.
[9]Weeks W F,W B Tucker,M Frank,et al.Characterization of surface roughness and floe geometry of sea ice over the continental shelves of the Beaufort and Chukchi seas[C]//R.S.Pritchard.Sea Ice Processes and Models,University of Washington Press,Seattle,1980:300-312.
[10]Holt B,Martin S.The effect of a storm on the 1992 summer sea ice cover of the Beaufort,Chukchi,and East Siberian Seas[J].Journal of Geophysical Research,2001,106(C1):1017-1032.
[11]Matsushita M.Fractal Viewpoint of Fracture and Accretion[J].Journal of the Physical Society of Japan,1985,54(3):857.
[12]Toyota T,Enomoto H.Analysis of sea ice floes in the Sea of Okhotsk using ADEOS/AVNIR images[C]//Proc.16th Int.Symposium on Ice,International Association for Hydro-Environment Engineering and Research,Dunedin,New Zealand,2002:211-217.
[13]Toyota T,Takatsuji S,Nakayama M.Characteristics of sea ice floe size distribution in the seasonal ice zone[J].Geophysical Research Letters,2006,33(2):87-94.
[14]Toyota T,Haas C,Tamura T.Size distribution and shape properties of relatively small sea-ice floes in the Antarctic marginal ice zone in late winter[J].Deep Sea Research Part II Topical Studies in Oceanography,2011,58(9):1182-1193.
[15]Lu P,Li Z J,Zhang Z H,et al.Aerial observations of floe size distribution in the marginal ice zone of summer Prydz Bay[J].Journal of Geophysical Research,2008,113(113):503-504.
[16]Steer A,Worby A,Heil P.Observed changes in sea-ice floe size distribution during early summer in the western Weddell Sea[J].Deep Sea Research Part II Topical Studies in Oceanography,2008,55(s 8-9):933-942.
[17]Stern H,A.Schweiger M Stark,J Zhang,et al.The Floe Size Distribution in the Marginal Ice Zone of the Beaufort and Chukchi Seas[C]//AGU Fall Meeting,2014.
[18]Soh L K,Tsatsoulis C,Holt B.Identifying Ice Floes and Computing Ice Floe Distributions in SAR Images[M].Analysis of SAR Data of the Polar Oceans,Springer Berlin Heidelberg,1998:9-34.
[19]Banfield J.Automated tracking of ice floes:a stochastic approach[J].IEEE Transactions on Geoscience&Remote Sensing,1991,29(6):905-911.
[20]Banfield J,Adrian E Raftery.Ice Floe Identification in Satellite Images Using Mathematical Morphology and Clustering about Principal Curves[J].Journal of the American Statistical Association,1992,87(87):7-16.
[21]Haverkamp D,Soh L K,Tsatsoulis C.A comprehensive,automated approach to determining sea ice thickness from SAR data[J].IEEE Transactions on Geoscience&Remote Sensing,1995,33(1):46-57.
[22]Wang Y,Holt B,Rogers W E,et al.Wind and wave influences on sea ice floe size and leads in the Beaufort and Chukchi Seas during the summer fall transition 2014[J].Journal of Geophysical Research,2016,121(2):1502-1525.
[23]Higashi A,Goodman D J,Kawaguchi S,et al.The cause of the breakup of fast ice on March 18,1980 near Syowa Station,East Antarctica[J].Memoirs of National Institute of Polar Research Special Issue,1982,24:222-231.
[24]Fox C,Squire V A.Strain in shore fast ice due to incoming ocean waves and swell[J].Journal of Geophysical Research Oceans,1991,96(C3):4531-4547.
[25]Meylan M,Squire V A.The response of ice floes to ocean waves[J].Journal of Geophysical Research Oceans,1994,99(C1):891-900.
[26]Perovich D K,Jones K F.The seasonal evolution of sea ice floe size distribution[J].Journal of Geophysical Research Oceans,2014,119(12):8767-8777.
[27]Burroughs S M,Tebbens S F.Upper-truncated Power Laws in Natural Systems[J].Pure&Applied Geophysics,2001,158(4):741-757.