In the summer, on the other hand, the warmest areas are the southernmost fragments of the continental Arctic, mostly the Russian Arctic and the Cana dian Arctic. Somewhat higher T values, however, occur in Canada due to the fact that the North American continent is surrounded in the north by a large number of islands forming the Canadian Arctic Archipelago.

In the summer, the low-lying areas of those islands are free from snow and absorb a significant amount of solar energy. Consequently, the air masses inflowing over the North American continent from the north are warmer than in the case of the Russian Arctic, which is surrounded by the cold waters of the Arctic seas covered with sea-ice, not far from the coastline (Barry et al. 1993). Air masses inflowing quite often from the north (where at this time there is a local high) lead to the cooling of those areas. As shown in Tables 5.2-5.4, the highest summer mean values of were noted at Mys Kamenny (6.6°C) and Coppermine (5.5°C); the highest summer mean values of T. occurred in stations Kanin Nos (11.2°C) and Coppermine (11.1°C); in the case of the highest summer mean values were observed in stations Coppermine (16.7°C) and Chokurdakh (15.5°C). Thus, the highest extreme T values occur in the same areas as their mean values.

In the summer, the coldest area is the Central Arctic, where the daily mean values of T oscillate around 0°C; this is connected with the fact that the advecting warmth is almost entirely used up in the process of melting snow and ice (CIA 1978). Mean extreme summer temperatures display similar behavioural patterns (cf. Figures 5.1 and 5.3). The lowest 40-year values are observed in the Central Arctic adjacent to ATLR and to the western part of the Siberian region (SIBR). Tmjn values oscillate between -2°C and 0°C and T values between 1°C and 3°C. The lowest values of the three thermal pa-

rameters discussed were observed in the regions directly adjacent to the Central Arctic (the stations Ostrov Vize, GMO E.K. Fedorova, and Ostrov Kotelny) (Tables 5.2-5.4). As can be inferred from Figures 5.1, 5.2, and 5.3, variability in T in the Arctic is greatest in winter and lowest in summer. The main factor responsible for this is the atmospheric circulation, which transports warmth from the lower geographical latitudes, mostly from the Atlantic and Pacific Oceans. As a result, in the regions of the Arctic adjacent to those oceans (and especially to the Atlantic) there occurs a significant deformation of the isotherms to the north.

Of particular interest are the changes in the spatial distribution of T in the successive decades of the period 1951-1990. In order to carry out an examination of this, the anomalies of annual mean T. values were plotted and, in the case of the last decade (globally the warmest during the period of instrumental observations), the anomalies were plotted additionally for all seasons (Figures 5.4 and 5.5). Moreover, it is only for this decade that maps are available showing the spatial distribution of the anomalies of and values for the winter, the

1 max mm summer, and the year as a whole (Figures 5.6 and 5.7). All anomalies were calculated with regard to the respective means from the period 1951-1990.

Figure 5.4. The spatial distribution of the anomalies of mean 10-year T. with regard to the 1951-1990 reference period mean in the Arctic. Negative anomalies are hatched.

For the warmest decade (1951-1960), positive anomalies of T. values prevailed, reaching their highest values in the central part of ATLR, where they exceeded 1°C. They were also high in the north-western part of the northern sub-region of the Canadian region (CANSRn) and on the south-eastern shore of Greenland (around 0.6°C). On average, it was colder than normal during this period, especially in the Pacific region (PACR) and in the small area of CANSRn adjacent to it. In Alaska, the anomalies reached around -0.6°C. Slight negative anomalies (up to around -0.2°C) were also noted in the southern part of the eastern sub-region of the Atlantic region (ATLSRe).

The 1960s saw a reversal in this situation (Figure 5.4) as the Arctic, similar to the rest of the globe, cooled considerably. In 70%-80% of the area there occurred negative anomalies of which reached their highest values in the central part of ATLR. It was there, in the late 1950s and the early 1960s, that the greatest cooling occurred - on average more than 2°C. Apart from this climatic region, significant negative anomalies were also observed in SIBR.

In the remaining area of the Arctic they were less significant, oscillating between 0°C and -0.2°C. Positive anomalies of T. (up to 0.4°C maximally) occurred in the strip of land stretching from Alaska to Baffin Bay.

Between 1971 and 1980 (Figure 5.4) negative deviations of T.still dominated, but their spatial distribution changed considerably. Most importantly, the central part of ATLR (including the whole island of Spitsbergen) warmed considerably and even some weak positive anomalies were noted. The strip of positive deviations of the previous decade, stretching from Alaska to Baffin Bay, disappeared. What is more, in this area, in the north-eastern part of CANSRn, the cooling was so great that it led to the greatest negative anomaly (exceeding -0.6°C). Another area where significant negative anomalies occurred was the southern part of ATLSRe (up to around -0.4°C).

Arctic temperature patterns underwent considerable changes in the 1980s. During this period, similar to the 1950s, positive deviations of T. dominated. The spatial distributions of those anomalies, however, are completely different and their values in the 1980s are much lower (Figure 5.4). It can be noted that in the areas characterised by negative anomalies in the 1950s, positive anomalies occurred in the 1980s, and vice versa. This may suggest that the mechanisms responsible for the warming in the two periods were different. Undoubtedly, anthropogenic factors exerted a greater influence on the climate in the 1980s than in the 1950s, most notably the emission of greenhouse gas-ses and aerosols into the atmosphere (see Karl et al. 1995, and others). It is worthwhile scrutinising the seasonal changes in T. in the 1980s (Figure 5.5). The comparison of the spatial distributions of the seasonal anomalies of shows that they are different. The greater part of the Arctic grew warmer in the spring and summer and, to a lesser degree, in the autumn also.

In all the seasons, negative deviations of T. were noted exclusively in BAFR (except for its northern parts in the summer). Cooling in this decade was also observed in the greater part of the Canadian region (CANR), except for the summer, when a slight warming occurred. PACR is characterised by positive anomalies in all seasons, except for autumn. The greatest positive deviations of were noted in SIBR in all seasons except summer. The least stable is ATLR, which in the cold half-year was characterised mainly by negative anomalies and in the warm half-year by positive ones (Figure 5.5).

In Figures 5.6 and 5.7, the spatial distributions of the anomalies of mean Tmax and Tm.n values for the years 1981-1990 are shown relative to the period 1951-1990 for the winter, summer, and the year as a whole. The greatest similarity of those distributions to the corresponding distributions of T. occurs in the winter and it is particularly strong between and (cf. Figures 5.5 and 5.6). The areas characterised by negative deviations of the extreme T values at that time were located over a large part of ATLR, in BAFR, and in the eastern part of CANR. The remaining part of the Arctic was characterised by T above the norm and the maximal warming (from 1°C to 1.5°C) was observed in the western part of SIBR, in Alaska, and in the Beaufort Sea.

In the summer, a significant similarity in the distributions of anomalies was observed between T. and Tmax (cf. Figures 5.5 and 5.6). It follows from the above that in the warm half-year the variability of T. is determined mostly by and in the cold period of the year it is determined mostly by

Figure 5.5. The spatial ditribution of the anomalies of mean seasonal T. in the 1980s, with reference to the 1951-1990 mean in the Arctic. Negative anomalies are hatched.

The distribution of the annual anomalies of T is more similar between T. and T (cf. Figures 5.4 and 5.7) than between T. and T .. T. differ from max ° y i mm mm other thermal parameters in that the negative anomalies in the 1980s occurred in the western part of SIBR and around the Pole. Some differences in the course of the isoanomalies between and may result from the fact that, in t max' mm J 7

the case of extreme temperatures, the data available came from fewer stations.

Particularly conspicuous is the lack of such data for the stations in Greenland (except for Danmarkshavn). Due to their poor quality, these data are not available at present. They will be employed only after the process of homogenisation has been completed (Frich - personal communication). For this reason, in Figures 5.6 and 5.7 the isoanomalies around the southern and south-eastern shores of Greenland were not plotted. However, it was assumed on the basis of the calculated anomalies of that the deviations of the extreme temperatures in this area should be of the same sign (±) as T. i.e. negative.

Figure 5.6. The spatial distribution of the anomalies of mean winter and summer Tmax (left panels) and T ln (right panels) in the 1980s, with reference to the 1951-1990 mean in the Arctic. Negative anomalies are hatched.

Summing up, it must be noted that the overall spatial distribution of thermal anomalies in the Arctic changed considerably over the successive decades. Even in the warmest and the coldest decades, the Arctic was not characterised exclusively by either positive or negative deviations (see also Figures 7.1 and 7.2). BAFR was characterised by the most stable trend in the changes of T. in the period 1951-1990. T. in this area consistently dropped throughout the period. In the southern sub-region of the Canadian region

(CANSRs) and in the southern part of ATLSRe, T. was below the norm for the greater part of the period under examination, In the former area, positive anomalies occurred in the 1950s, while in the latter area such anomalies were noted in the 1980s. The most sensitive area to climatic changes is ATLR, especially its central and eastern parts and the north-eastern part of CANSRn. ATLR, except for its western and eastern parts, has not exhibited major changes in Tin the last 20 years (Figure 5.4; see also Przybylak & Usowicz 1994).

Figure 5.7. The spatial distribution of the anomalies of mean annual Tmax (upper map) and T (lower map) in the 1980s, with reference to the 1951-1990 mean in the Arctic. Negative anomalies are hatched.

It is worth investigating how the spatial distribution of the anomalies of T. changed in the decades preceding the period under examination. Unfortunately, there were far fewer Arctic stations at the beginning of the 20th century. This is why the tracking of those changes is possible for only 8 stations from the 1920s onwards, and for another 2 stations from the 1930s (Table 5.5). Obviously, it is not possible to represent this phenomenon carto-graphically, as was done for the period 1951-1990. As the table shows, between 1921 and 1950 the mean T. for the Arctic was above the norm. It was i warmest in the 1930s (annual anomalies were around 1.0°C). This is also confirmed by the data published by Alekseev and Svyashchennikov (1991), Dmitriev (1994) and those made available by Jones (personal correspondence). These data are represented graphically in Figure 5.12. The greatest warming occurred in the winter and autumn. In the summer, on the other hand, even negative deviations were observed (in the 1920s and 1940s). These conditions prevailed throughout the greater part of the Arctic, with the possible exception being CANR in the period 1921-1940 (CANR is represented in Table 5.5 only by the Coppermine station). PACR (station Barrow) was also characterised by a slight warming. The greatest T. occurred mainly in ATLR, though T. values were also quite high in BAFR. In ATLR and SIBR, similar to the mean temperature of the Arctic the warming in the course of the year was greatest in the winter and autumn; in BAFR, the greatest warming occurred in the spring and summer, and in CANR in the winter and spring. In PACR in subsequent decades, various seasons were characterised by higher than the norm.

Table 5.5. Seasonal and annual anomalies of 10-year 7* (in °C) in selected Arctic stations with the longest data series and for averaged Arctic T with reference to the mean 1951-1990*


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Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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