In recent years, a number of studies have examined climate change across the Antarctic using station observations. Jacka and Budd (1998) used data from 1956 to the late 1996 and found a warming of 0.12°C per decade. A further study of trends in Antarctic near-surface temperatures was carried out by Jones (1995). He considered the temperature records from 16 stations that covered 1957-94 and found an increase of 0.57°C over this period, which was statistically significant at <5 per cent level. This rate of change is of the same order of magnitude as reported by Jacka and Budd (1998).
Doran et al. (2002) derived annual and seasonal temperature trends for Antarctica and claimed that there has been a net cooling of the entire continent over the period. Turner et al. (2002) argued that it was not possible to derive a trend for the whole continent. Turner et al. (2005) studied 50 years’ data of 19 stations and computed trends for surface temperature, mean sea level pressure and wind speed and indicated that the spatial complexity of temperature change that has occurred across the Antarctic during recent decade. The data considered were for the stations with long records only (1951-2000). The trends were computed using a standard least square method. They pointed out that Novolazarevskaya has warmed at a rate of 0.25°C per decade over the period 1962-2000 which is significant at 10 per cent level. Clearly more work is needed on this decadal time scale variability of temperatures over East Antarctica.
The Schirmacher Oasis is one of the smallest East Antarctic oases of Queens Maud Land area. It has a maximum width of 3.5 km and a length of about 20 km. It is oriented approximately in an east-west direction with approximate area of about 35 sq. km. The coordinates of the oasis are (70o 46’ 04” – 70o 44’ 21”) S and (11o 49’ 54” – 11o 26’ 03”) E (Figure 1). The elevation of oasis ranges between 0 to 228 m with an average of 100 m. There is a 200 to 500 m thick and about 100 km wide ice shelf slab north of Schirmacher oasis and approximately 1000 m thick and 50 km wide firn basin glacier in the south. On the southern edge of the Schirmacher oasis, it terminates as a 10 to 40 m high escarpment while it shows a smooth transition to ice shelf both east and west of the area.
Indian Antarctic Station, Maitri (70o 45’ 57” S/11o 44’ 09” E) (Figure 2) was established in 1989 in the Schirmacher Oasis of East Antarctic. It was occupied as a summer campsite in 1985 and later converted as second permanent station during the Indian Antarctic Expedition on 9th March 1989. The elevation of the station is 117 m above mean sea level. Russian Antarctic Station, Novolazarevskaya (70°46’04” S and 11°49’54” E) (Figure 3) is situated over the Schirmacher region, Princess Astrid Coast, East Antarctica. It was opened on January 18, 1961 by the 6th Soviet Antarctic Expedition. The elevation above sea level is 102 m.
Bharati is an upcoming and third Research station commissioned by India at Antarctica. It will be the third and second active research station along with Maitri (active) and Dakshin Gangotri (abandoned, but used as a supply base) for India. India has demarcated an area beside Larsemann Hills at 69°S, 76°E (Figure 4) for its third settlement and second active research station. The station is scheduled to be operational by 2012. With the commissioning of this station India has entered the elite group of nine nations having multiple stations within the Antarctic Circle.
In February 1989, a Chinese National Antarctic Expedition constructed the Zhongshan Meteorology Observatory (69o22’ S, 76°22’ E, 15 m above sea level) on Larseman Hill in Prydz Bay on the eastern Antarctic continent. Meteorological data of the station is available from Reference Antarctic Data for Environmental Research (READER) project data base and also from data base of Chinese Academy of Meteorological Sciences. The details of the READER data collected and quality control of the observations are described in detail in Turner et al. (2004).
The location of all three stations under study is shown in Figure 5. In this paper, the variation in mean air temperature and its trends are derived from the meteorological observation data recorded at the Maitri, Novolazarevskaya and Zhongshan station from 1990 to 2011.
Material and Method
Surface air temperature of Maitri (MAT) was obtained from archives of IMD for the period 1990-2011. The daily mean values were derived by averaging eight three hourly synoptic observations. Thereafter monthly and annual values were calculated. The mean monthly temperature of Novolazarevskaya (NOVO) for the period of study was obtained from the Russian Federation, NADC, Arctic and Antarctic Research Institute (AARI) website http://www.aari.aq. The mean monthly temperature of Zhongshan (ZS) for period 1990-2007 was obtained from the website of Chinese Academy of Meteorological Sciences. Data for remaining period (2008-2011) was obtained from the READER data set. The monthly mean air temperature data are presented as daily mean values derived from data recorded at 00:00, 00:06, 12:00, and 18:00 UTC each day for Novolazarevskaya and Zhongshan.
To consider the change characteristics of seasonal mean temperatures at both stations, the mean temperatures in spring (SON), summer (DJF), autumn (MAM) and winter (JJA) are obtained from the data set. Five sets of mean temperature were obtained from these monthly means. Annual, Summer (DJF), Autumn (MAM), Winter (JJA) and Spring (SON) temperature and their standard deviation is shown in Table 1. Trends were computed using a standard least square method. Monthly mean temperature of all three stations is shown in Table 2 and Figure 6.
Result & Discussion
Monthly mean air temperature
The data from Table 1 indicates the characteristics of the average annual cycle are that the maximum monthly mean temperature is in January and lowest mean monthly temperature in the month of August with annual range of 17.94 (MAT), 17.15(NOVO) and 16.47 (ZS). As shown in Figure 6 the annual cycle variation in temperature at the all three stations indicates a coreless winter and pointed summer.
Trend of change in air temperature
Figure 7 shows the time series of the monthly mean temperature for NOVO, MAT and ZS for the period 1990-2011. The trend of the change in air temperature can be represented by a trending coefficient, change rate, and difference in mean values of the former and latter periods. The trend indicates the cooling at Maitri and Novolazarevskaya whereas Zhongshan shows a rising trend during the period of study. Variation of mean annual surface air temperature from normal as derived from the data under study is shown in Figure 8. The data indicates that interannual mean air temperature varies within 1oC except for some years when large variations were observed. Such variations are due to influence of synoptic systems which controls the surface temperature variations.
Trend in seasonal air temperature
Figure 9 and 12 present the inter-annual change and trend of the seasonal mean temperature for the three stations. The inter-annual fluctuations of the seasonal mean temperature of these stations are both large; nevertheless, there are apparent differences in the trends. From Figure 9 and Figure 11 it is clear that all stations show a cooling trend during the period of study but cooling trend at Zhongshan station during summer is very small in comparison to the other two stations.
The variation in mean air temperature and its trends derived from the meteorological observation recorded at the Maitri, Novolazarevskaya and Zhongshan station from 1990 to 2011 indicates that the cooling rate at Maitri is similar to that at Novolazarevskaya station, which is about 3 km away and the recent cooling trend is representative of the Schirmacher Oasis region. The annual mean temperature of Zhongshan station indicates a small rising trend.
It can be said that the meteorological data recorded at these stations are representative of the regions of east coast of the Antarctica and reflect the climate change characteristics on a large scale without an apparent warming trend on the east Antarctic continent. The analysis provides the basic characteristics of temperature change for further application of meteorological data recorded at these Antarctic stations and research into the process of Antarctic climate change and its role in global change.
Authors are thankful to the Director General of Meteorology, India Meteorological Department, Arctic and Antarctic Research Institute (AARI), Russia and Chinese Academy of Meteorological Sciences for facility extended for use of Meteorological data from their data bases. The efforts put up by all members of meteorological community of Indian, Russian and Chinese Antarctic Expedition team for taking meteorological observations under adverse hostile environmental conditions are also acknowledged. Without their contribution this study was not feasible.
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