IGOR POLYAKOV

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Variability and trends of air temperature and pressure in the maritime Arctic, 1875 - 2000

Igor V. Polyakov¹, Roman V. Bekryaev^1,2, Genrikh V. Alekseev²,
Uma Bhatt¹, Roger L. Colony¹ , Mark A. Johnson³,
Alexander P. Makshtas¹, and David Walsh¹

¹International Arctic Research Center, University of Alaska Fairbanks
²Arctic and Antarctic Research Institute
³Institute of Marine Science, University of Alaska Fairbanks

Despite the significant body of research and a preliminary understanding of driving mechanisms of the recent observed changes in the Arctic, there is still a large degree of uncertainty about the role of natural low-frequency variability and trends. The goal of this research is to assess long-term (century plus) arctic air temperature and pressure trends and their low-frequency variability using available observational data from around the entire Arctic. (Details of this research may be found in [Polyakov et al., 2002a, 2002b]).

We examine arctic surface-air temperature and pressure data for the period 1875-2000 using long-term records from the maritime Arctic, poleward of 62N. These long-term records are now available due to recently released Russian meteorological observations poleward of 62N. We chose the best 75 stations (Figure 1) from about 200 available land meteorological stations, maintaining approximately homogeneous spatial coverage and omitting records with gaps. Twenty-four records are longer than 100 years, thirty-one other records are longer than 65 years, observations from twenty stations cover less than 65 years with the shortest having 43 years. In order to eliminate site density bias, we omitted data before 1875 because only a few time records, mostly from Scandinavian stations, extend to earlier years. Fortunately, the remaining geographical bias in the early part of the composite time series is relatively small [Polyakov et al., 2002a].

Two composite monthly time series, one for SAT and another for SLP for the area poleward of 62N elucidate the Arctic and sub-Arctic atmospheric variability (Figure 2). Arctic air temperature and pressure display substantial variability on time scales of 50-80 years. The multidecadal variability (LFO) is evident in various instrumental and proxy records for the Northern Hemisphere. This variability appears to originate in the North Atlantic and is likely induced by slow changes in oceanic thermohaline circulation [Delworth and Mann, 2000]. However, SAT records demonstrate stronger multidecadal variability in the polar region than in lower latitudes. This may suggest that the origin of this variability may lie in the complex interactions between the Arctic and North Atlantic. Associated with the LFO, SAT record shows two periods of highest temperatures in the Arctic: in the 1930-40s, and in recent decades. In contrast to the global and hemispheric temperature, the maritime arctic temperature was higher in the late 1930s-early 1940s than in the 1980-90s.

The composite temperature record shows that since 1875 the Arctic has warmed by 1.2C, so that over the entire record the warming trend was 0.094C/decade, with stronger spring- and winter-time warming (Figure 3). The arctic temperature trend for the twentieth century (0.05C/decade) was close to the Northern Hemispheric trend (0.06C/decade). The oscillatory behavior of arctic trends results from incomplete sampling of the large-amplitude LFO. For example, the arctic temperature was higher in the 1930-40s than in recent decades, and hence a trend calculated for the period 1920-present actually shows cooling. Enhancement of computed trends in recent decades can be partially attributed to the current positive LFO phase.

We speculate that warming alone cannot explain the retreat of arctic ice observed in the 1980-90s. Also crucial to this rapid ice reduction was the low-frequency shift in the atmospheric pressure pattern from anticyclonic to cyclonic (see also [Polyakov and Johnson, 2000; Proshutinsky and Johnson, 1997]). Positive and negative LFO phases of the SAT are shifted by 5-15 years relative to those in the SLP record. The complicated nature of arctic temperature and pressure variations makes understanding of possible causes of the variability, and evaluation of the anthropogenic warming effect most difficult.

Available on web: SAT and SLP data

Composite time series of the arctic (north of 62N) SAT (degC) and SLP (mb) anomalies are also available on web (download the data now). The form of the file is self-explanatory.

References

Delworth, T. L., and M. E. Mann, Observed and simulated multi-decadal variability in the Northern Hemisphere, Climate Dynamics, 16, 661-676, 2000.

Polyakov, I., and M. A. Johnson, Arctic decadal and inter-decadal variability, Geophys. Res. Lett., 27, 4097-4100, 2000. [download pdf]

Polyakov, I. V., G. V. Alekseev, R. V. Bekryaev, U. Bhatt, R. L. Colony, M. A. Johnson, V. P. Karklin, A. P. Makshtas, D. Walsh, and A. V. Yulin, Observationally based assessment of polar amplification of global warming, Geophys. Res. Lett., 29, 1878, doi:1029/2001GL011111, 2002. [download PDF file]

Polyakov, I. V., R. V. Bekryaev, G. V. Alekseev, U. Bhatt, R. L. Colony, M. A. Johnson, A. P. Makshtas, and D. Walsh, Variability and trends of air temperature and pressuremin the maritime Arctic, 1875-2000, J. Climate, 16(12), 2067-2077, 2003.[ download PDF file]

Proshutinsky, A. Yu., and M. A. Johnson, Two circulation regimes of the wind-driven Arctic Ocean, J. Geophys. Res., 102, 12493-12514, 1997.

Last modified: May 06, 2004. 14:56:48 pm