东西伯利亚海海冰季节变化特征及主要影响因素分析

利用1997-2005年美国国家冰雪中心提供的卫星遥感数据,对东西伯利亚海海冰周年变化特征及其动力和热力学机制进行详细分析,以1999年海冰状况为例讨论了该海域海冰的周年变化。按照海冰变化的区域特征和融化机制差异,将全年的海冰变化过程分为密集冰封期、陆坡开裂期、西部融化期、全面融化期和秋季结冰期。不同年份各个阶段发生的具体日期不尽相同,海冰覆盖面积最小值及其发生时间有所差异,但是,各年海冰变化的5个阶段都清晰可辨。海冰融化时间持续3个月,冻结时间仅为1个半月左右。每年5月份东西伯利亚海陆坡处海冰发生开裂,主要是该时期风场辐散的作用。1999年,除5月份以外的其他月份,东西伯利亚海海表面风场是辐聚风场,不利于海冰融化和开阔水域面积的扩大。东西伯利亚海海冰融化的决定性因素是陆地径流,因迪吉尔卡河、科雷马河、亚纳河和勒拿河四条河流在海冰融化过程中发挥主要作用。海冰覆盖面积最小值出现的时间一般是9月下旬,整个海域的沿岸带海冰全部消失,形成大范围的开阔水。夏季北半球气温的升高和太阳辐射的加热作用,为海冰融化提供持续的热量。

SEASONAL VARIATIONS OF SEA ICE COVER IN THE EAST SIBERIAN SEA AND ITS MAIN DRIVING FACTORS

Seasonal variation of the sea ice concentration as well as its dynamical and thermodynamical forcing mechanism in the East Siberian Sea are studied in detail using the satellite remote sensing data during 1999—2005 provided by National Snow and Ice Data Center of USA.The analysis for 1999 sea ice condition reveals that the annual variation of sea ice cover can be divided into 5 stages,namely,packed ice,broken belt along the continental slope,western melting,all-sea ice melting and autumn freezing.The annual five stages are distinguishable clearly,although the minimum of the sea ice cover and appearing date are different each year.The freezing period lasted only 1.5 months,whereas the melting process spent about three months.A sea-ice-rupture area happened in May along the continental slope of the East Siberian Sea due to wind field's divergence.However,the wind field went against the sea ice melting and freezing at the rest of 1999.The runoffs,especially from Indigirka River,Kolyma River,Yana River and Lena River,are the key factors for sea ice melting in the East Siberian Sea.The minimum of the sea ice cover appeared in the late September,in which there wasn't sea ice any more along the coast and a large area of open water formed.In the Northern Hemisphere,the solar heating and air temperature rising provided heat energy continuously for the sea ice melting.