巴伦支海海冰多年变化及其影响因子研究

Study on the Multiyear Variations of Sea Ice in the Barents Sea and Its Influencing Factors

本文采用1900—2010年ECMWF海冰密集度、海面温度、风场和NCAR北极涛动等长序列资料,运用EOF分解、线性回归和相关分析等统计方法,分析了巴伦支海海冰年际变化特征及其与影响因子之间的关系。结果表明:巴伦支海海冰面积4月最大,9月最小,每年减少约1653km^2;面积距平正负位相交替出现,1969年后以负距平为主,冰情先重后轻;密集度逐月不同,明显降低的区域呈现“中部偏东—中部—东北部—西北部—中部偏东”转移特点,部分区域每年减少0.006以上;密集度变化的空间特征可由密集度EOF第一主模态表示,与温度的相关系数高于风场;海冰面积与AO呈负相关。我国以往单独针对巴伦支海海冰变化的研究较少,本文丰富了这方面的资料,对浮式平台开发冰区油气资源提供初步参考。

During the past few decades,the Arctic Ocean has experienced clearly climatic changes,especially manifested by its plummet of sea ice cover.The Barents Sea is an important marginal sea of the Arctic Ocean and is a significant zone with sea ice anomaly in Arctic.In this paper,multiyear variations of sea ice area and its relationships with climate factors over the years(1900-2010)are studied with the methods of empirical orthogonal function(EOF)decomposition,linear regression and correlation analysis based on long-time data series such as Sea Ice Concentration,Sea Surface Temperature,Wind from ECMWF and NCAR.Results show that the average sea ice area in the Barents Sea reaches the largest in the April and decreases to the lowest in the September,and the rate of average sea ice area reduction is higher than in the Pacific Sector of the Arctic with a value of-1 653 km^2 per year.Over the entire period the area anomaly alternates with positive and negative phase,but from 1969 until now the negative ones are the main patterns,revealing that ice condition in the Barents Sea underwent a shift from heavy-ice to light-ice years.In addition,the spatial distributions of sea ice edge have obvious seasonal variation characteristics.In winter the north of the Barents Sea exists high concentration ice where the SIC can be more than 0.9 and a large number of ice appears in the southeastern sea.In summer the original high concentration ice melts and the ice edge retreat greatly and in the southeast there is no ice absolutely.We also find that sea ice concentration where reduces distinctly is different from month to month,showing a periodic shift of‘middle east-central-northeast-northwest-middle east’.In some zones the sea ice concentration can even reduce 0.006 per year.The figures from No.5 to No.6 show these variations clearly.Furthermore,the decreasing of sea ice concentration can be better represented by its first leading EOF mode(see Fig.7b),which the contribution rate of the total variance is higher than 40%.The EOF1 patterns show that the values are all of the same phase distribution with only one unipolar point,in particular,the higher values zones in EOF1 are exactly consistent with sea ice concentration where reduce largely in Fig.6.In details,the changes are significantly or highly correlated with sea surface temperature and are relatively low correlated with wind field,the correlation coefficients of which all pass the test with a significance level of 0.05.Thus the sea ice sensitivity of temperature is highly than wind.The movement of the sea ice is inconsistent with the wind probably due to the interruption and deformation of wind drive.It is also paid attention to that the correlations of sea ice concentration with zonal wind and meridional wind are weaker than values with total wind speed.We firstly present the statistical phenomenon however no precise mechanism until now can make it completely clear.Besides,the correlation coefficient between sea ice area and AO is negative.The sea ice area increases when AO is negative while declines when AO is positive.In a nutshell,the joint effects of thermodynamics and the dynamics contribute to the spatial and temporal changes of sea ice concentration.There is few in our country to separately analyze the sea ice in the Barents Sea,therefore this paper enriches the knowledge of this specifying sea and provides a certain reference for the ice zone partition in the Barents Sea and for floating platforms to explore the oil and gas in ice zones by determining operation time and area in engineering.