Variability and Trends of Air Temperature and Pressure in the Maritime Arctic, 1875-2000

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Variability and Trends of Air Temperature and
Pressure in the Maritime Arctic, 1875-2000

• Air Temp. and press. show strong multidecadal
  variability on timescales of 50-80 yrs Low
  Frequency Oscillation (LFO)
• Surface albedo, greenhouse gases, and cloud
  cover can amplify the LFO (shown in GCMs)
• there is still a large degree of uncertainty
  about the role of natural low frequency
  variability and trends ??

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Data

• Datasets of monthly SAT/SLP are from many
  different places in the Northern Hemisphere
• SAT/SLP time series, data was from stations
  north of 62N only
• Used best 75 of 200 land stations (omitted data
  pre-1875)
• The goal of the data set was to get a single
  time record of monthly SAT/SLP that could explain
  the Artic/Sub-Arctic air temp and press
  variability.

Figure 1
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Low-frequency variability

• SAT shows 2 negative (cold) and 2 positive
  (warm) phases of LFO
• Using 1875-2001 Arctic SAT data, a stronger LFO
  in polar regions compared to low latitudes.
  Supported by Arctic coastal stations and the
  North Atlantic Oscillation (NAO).
• Higher temps in 1930s-40s and lower temps in
  1960s-70s are associated with the pos and neg LFO
  phases
• SAT/SLP variablilty show strong seasonality,
  with stronger in cold season and weaker in the
  warm season.
• Changes in Arctic atmospheric circulation have
  large impact of Arctic ice conditions. Cyclonic
  circulation causes increased wind vorticity that
  favors thinner ice and ice drifting.
  Anticyclonic causes decreased vorticity that
  favors convergent ice producing thicker ice.
  (today we have cylconic vorticity)

Figure 2,3,4,5
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Trends

• Since 1875, Arctic is warming at rate of
  .09C/decade
• Compared to overall Northern Hemisphere trend,
  Artic SATs increase twofold from 1875-2001.
  Vinnikov et al. (1980) also found this twofold
  polar amplification from 1891-1978
• Arctic SAT trends depend on phases and
  intensity of the LFO with any long-term trends.
  Northern hemisphere don not show this dependence
  on the LFO.

Figure 2,6 Table 1
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Conclusions

• Arctic air temp and press display a substantial
  variability on 50-80 yr timescales.
• SAT trends are stronger in the polar regions
• Arctic has warmed by 1.2C since 1875
• 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

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Jones et al. 1999
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Arctic Oscillation (AO)
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North Atlantic Oscillation (NAO)