Variation Of Sea Ice Thickness And Area In The Ross Sea

Sea ice thickness is an important climatic indicator. It is a hot topic to obtain itsspatial and temporal variations under circumstance of the sea ice monitoring andforecasting in polar regions. In this paper, the ICESat/GLAS laser altimeter data wereused to retrieve the sea ice thickness (SIT) in the Ross Sea, then sea ice concentrationand NCEP atmospheric dataset were used to analyze the relationship between sea icevariations and processes of the atmospheric and oceanic system.Sea ice thickness and area had remarkable seasonal and inter-annual variations inthe Ross Sea. The seasonal variations of the sea ice thickness were exhibitedgeophysically. The probability distribution functions illustrated that the SITconcentrated in the1.0-2.8m,0.6-1.8m and1.0-2.2m in the three campaign periods(FM, MJ, ON). The mean SIT was thin (1.3±1.0m) in May-June, and thick inFebruary-March (1.9±1.5m).Inter-annual variations of sea ice thickness were also found in the Ross Sea. Seaice thickness showed different characteristics in different seasons. The inter-annualrange of SIT in FM was significant compared to the other two seasons, and exhibiteda increasing trend for thicker sea ice. Compared with FM and MJ, sea ice thicknessdecreased in the last five years (2004-2008). The sea ice edge aligned along zonal linewith little spatial variance.Meanwhile, the sea ice area also had seasonal and inter-annual variations. Itsminimum was in February, and maximum in September. In summer (DJF) there had awide range in the open water of the southern part of the Ross Sea; in autumn (MAM)the sea ice intensity is greater from west to east. Sea ice outside edge lines in winterand spring are paralleled to64°S. In winter and spring, the inter-annual variations ofsea ice area were significant,30.5±2.6×105km~2and31.7±2.5×105km~2, respectively.Sea ice area in Ross Sea had a significant increase in the fall, and its secular trend was1.3×104km~2/yr during the past30years (1979-2010). Sea ice volume was derived based on the sea ice thickness and area in the RossSea. The average values of the sea ice volume were2461km3,5250km3, and9586km3during the three campaign periods. The inter-annual variation of February-March andOctober-November were significant, and their trends were almost opposite, theyreached the extreme value around2006. Moreover, sea ice volume increasedmonotonously in the last three June-July seasons.Sea ice area in the Ross Sea had closed relationship with the air temperature andsea level pressure in the equatorial Pacific Ocean. Their correlation coefficientillustrated the opposite pattern zonally. The positive correlation coefficients reached0.6when sea ice area led the SO index about two months, which the inter-annualsignal with significant period of2-8years were obtained in the both series.Composite analysis method was used to grasp the planetary thermodynamicatmospheric processing responding to the sea ice area variation. It was shown whensea ice area increased, the positive sea level pressure anomaly occurred along the westcoast of the South America, accompanied with a counterclockwise surface windanomaly in the subtropical anticyclonic circulation. Then cold air convectionappeared two months later in the east of the south Pacific Ocean (10-40oS), whichwas subject to maintain the cold atmospheric anomaly in eastern equatorial Pacificand support the developing of the La Nina event.