1979-2018年南极海冰边缘区范围时空变化研究

Analysis of temporal and spatial changes in the extent of the Antarctic marginal ice zone from 1979 to 2018

南极海冰边缘区是海洋-大气的重要交换区,也是海洋生物的重要栖息地,其年际变化、季节性变化和区域差异显著影响着全球海洋和大气环境。基于美国国家冰雪数据中心1979—2018年的海冰密集度数据集,本研究将海冰密集度15%~80%作为阈值确定海冰边缘区,通过边缘区范围的年际变化、季节性变化来分析整个南极及其5个子区域的海冰边缘区范围时空变化特征与趋势。研究结果表明,南极海冰边缘区所在的位置并不稳定,大部分边缘区海冰出现的频次小于20年。40年间南极海冰边缘区范围呈略微减少趋势,减少速度为(5.8±2.6)×10^(3) km^(2)·a^(–1)。边缘区平均纬度并没有明显偏移趋势。此外南极海冰边缘区范围和平均纬度呈现稳定的季节性周期变化,边缘区范围于2月达到最小值,在3—11月缓慢增长,12月到达最大值后迅速下降。边缘区平均纬度通常在9月到达最北端,2月到达最南端。此外,5个地理分区中威德尔海扇区的边缘区范围最大,波动最明显,平均纬度最偏北。5个分区的年平均边缘区范围和平均纬度的变化趋势在1979—2018年间整体较为平缓,但是边缘区范围和平均纬度的变化趋势分别在1979—1988年间和1999—2018年间最为明显。

The marginal ice zone(MIZ)around Antarctica is an important ocean-air interaction zone and a crucial habitat for marine life.Its annual,seasonal,and regional variations significantly affect the global ocean and atmospheric environments.Based on the sea ice concentration data set of the National Snow and Ice Data Center from 1979 to 2018,the MIZ is defined by a sea ice concentration threshold between 15%and 80%.In this study,we investigated the spatiotemporal variation of the extent of the MIZ,and analyzed its interannual and seasonal changes over the entire Antarctica and its five subregions.Results show that the Antarctic MIZ is not stable,and most of the sea ice in MIZ is less than 20 years.Over the past 40 years,the MIZ extent slightly decreased at a speed of 5.8±2.6×10^(3) km^(2)·a^(−1)(P<0.05),although the MIZ average latitude showed no significant trend.Both the MIZ extent and average latitude exhibited stable periodic variations.The MIZ extent is minimal in February,but increases from March to November,decreasing rapidly after reaching its peak in December.The average latitude of the MIZ is northernmost in September and southernmost in Feb-ruary.The MIZ extent in the Weddell Sea is largest among Antarctic sub-regions,where the fluctuations are most obvious and the average latitude is more north.The MIZ extent and average latitude in the five sub-regions are stable during 1979-2018,but the trends of those are the most obvious during 1979-1988 and 1999-2018,respectively.