北极海冰快速变化及大气优势模态的响应

发布时间：2018-04-11 05:15

本文选题：北极海冰 + 季节变化　；参考：《中国海洋大学》2014年硕士论文

【摘要】：本文采用美国冰雪中心以及欧洲哈德莱数据中心的海冰密集度数据，，详细分析了1979年至2012年34年间北极海冰的变化特征。研究结果表明，北极海冰正在经历着一个快速变化的过程，海冰覆盖范围整体呈现减少趋势，但存在两次年代际转型，主要变化特征分为三个阶段：①1979年~1996年，②1997年~2006年，③2007年~2012年。第一阶段海冰线性减少趋势相对较小，年际振荡振幅适中；进入1997年之后，北极海冰快速减少，其线性减少趋势达到之前的三倍以上，但年际振荡振幅很小；在2007年之后，北极海冰线性减少趋势不显著，但振幅急剧增加。空间上，海冰变化中心区域逐渐由边缘海区向北极中央海区扩展。与此同时，季节变化特征明显改变：融冰开始时间提前，结冰时间推后，融冰期时间延长，季节振荡加剧。此外，随着北极整体海冰的减少，北极中央区海冰近些年来也呈现出不断减少的趋势。通过数值试验分析大气对于北极海冰快速变化的异常响应，我们发现：随着北极海冰的逐渐减少，会引起北极局地明显的升温现象，同时导致局地海平面气压降低，而中纬度地区海平面气压场升高。而海冰的变化还会直接影响到北极涛动（AO）和偶极子型（DA）的改变。从模式结果来看，随着北极海冰的逐渐减少，北极涛动逐渐向正位相偏转，同时极端AO发生频率增加，平均强度增大。这有可能导致中高纬度大气振荡加剧，极端天气现象发生概率增加。为研究未来北极海冰的变化特征，综合考虑北极海冰的变化特征，采用四个独立的指标描述模式对海冰的模拟性能，建立了一套全新的模式评价标准，从31个含有海冰模块的第五次耦合模式比较计划（Coupled Model IntercomparisonProject Phase5，CMIP5）模式结果中筛选出6个能够很好地模拟出北极海冰历史变化特征的数值模式，并以此为基础，研究未来北极海冰的变化特征。结果表明，北极海冰最早可能在2040年之前达到夏季无冰现象，即所有多年冰消失，全部转化为一年冰，同时海冰范围变化的振幅急剧增加。在极端情况下（RCP8.5情境），至本世纪末，融冰期由目前的每年7月中旬开始10月结束转变为每年4月开始次年1月结束，融冰时间延长近200天。同时，北极海冰变化也由边缘海区向北极中央海区扩展，到本世纪末，海冰变化的中心区域可能位于北极点附近。同时，根据模式结果预测，未来的北极涛动有向正位相转变的倾向。
[Abstract]:Based on the ice intensity data from the American Ice and Snow Center and the European Hadley data Center, the variation characteristics of Arctic sea ice from 1979 to 2012 are analyzed in detail.The results show that the Arctic sea ice is undergoing a rapid change process, and the sea ice coverage has a decreasing trend, but there are two Interdecadal transformations, the main characteristics of which are divided into three stages: 11979 ~ 1996, 21997 ~ 2006.3 from 2007 to 2012.In the first stage, the trend of linear decrease of sea ice was relatively small, and the amplitude of interannual oscillation was moderate. After 1997, the Arctic sea ice decreased rapidly and its linear decreasing trend reached more than three times the previous trend, but the amplitude of interannual oscillation was very small; after 2007,The linear decreasing trend of Arctic sea ice is not significant, but the amplitude increases sharply.In space, the sea ice change center area gradually extends from the marginal sea area to the Arctic central sea area.At the same time, the characteristics of seasonal variation are obviously changed: the beginning time of melting ice is early, the time of ice formation is delayed, the time of melting ice period is prolonged, and the seasonal oscillation is intensified.In addition, with the decrease of the whole Arctic sea ice, the Arctic central sea ice also shows a decreasing trend in recent years.Through numerical experiments to analyze the anomalous response of the atmosphere to the rapid change of Arctic sea ice, we find that with the gradual decrease of Arctic sea ice, the local warming phenomenon in the Arctic will be obvious, and the local sea level pressure will decrease at the same time.And the sea level pressure field increases in the middle latitudes.The changes of sea ice also directly affect the changes of AOA and DAA.From the results of the model, with the decrease of Arctic sea ice, the Arctic Oscillation gradually deflects to the positive phase, at the same time, the frequency of extreme AO increases and the average intensity increases.This may lead to the increase of atmospheric oscillation and the probability of extreme weather phenomena in the middle and high latitudes.In order to study the variation characteristics of Arctic sea ice in the future, considering the variation characteristics of Arctic sea ice, four independent indexes are used to describe the simulation performance of sea ice, and a set of new model evaluation criteria are established.From the results of the fifth coupled Model IntercomparisonProject phase 5 CMIP5 model with sea ice modules, six numerical models were selected to simulate the historical variation characteristics of Arctic sea ice.The variation characteristics of Arctic sea ice in the future are studied.The results show that the Arctic sea ice may reach the summer ice free phenomenon as early as 2040, that is, all years of ice disappear, all of them are converted into one year ice, and the amplitude of the range of sea ice changes increases sharply.In extreme cases, by the end of this century, the melting ice age has changed from the beginning of October to the end of each year from the middle of July to the end of January of the following year, and the time of melting ice is extended by nearly 200 days.At the same time, the variation of Arctic sea ice extends from the marginal sea area to the central Arctic sea area. By the end of this century, the central area of the sea ice change may be located near the Arctic point.At the same time, according to the model results, the future Arctic Oscillation tends to shift to positive phase.
【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P731.15;P461.2

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