Research ArticleCLIMATOLOGY

Extensive fires in southeastern Siberian permafrost linked to preceding Arctic Oscillation

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Science Advances  08 Jan 2020:
Vol. 6, no. 2, eaax3308
DOI: 10.1126/sciadv.aax3308
  • Fig. 1 Fire activity over southeastern Siberia.

    (A) Mean burned area fraction (% year−1) over mid- and high latitudes in the Northern Hemisphere. Hatched areas indicate permafrost regions. The black box indicates the study area in southeastern Siberia (100°–150°E, 45°–55°N). (B) Monthly burned area (Mha month−1) in southeastern Siberia for 1997–2016 in each year (gray), mean (thick black), composite for February to March AO index > 0.5 SD cases (red), and AO < −0.5 SD cases (blue). (C) Mean burned area according to February to March AO index (orange) and 850-hPa geopotential height anomaly over southeastern Siberia (red). Bins on the x axis indicate <20%, <40%, <60%, <80%, and <100% rank ranges.

  • Fig. 2 Atmospheric circulation related to fire activity in southeastern Siberia.

    Regression coefficients of temperature (shading), 850-hPa geopotential height (contour; 100-gpm interval), and 850-hPa wind (vector) for February (A), March (B), April (C), and May (D) on normalized yearly burned area in southeastern Siberia (boxed area). The climatological 0°C line for 2-m temperature is shown as a thick yellow line. Wind vectors are displayed only in regions significant at the 95% confidence level based on Student’s t test.

  • Fig. 3 Snow cover variation related to fire activity over southeastern Siberia.

    Climatological monthly snow cover (shading) and statistical confidence (dots) based on correlation coefficient between yearly burned area in southeastern Siberia (boxed area) and monthly snow cover anomalies for February (A), March (B), April (C), and May (D) based on Student’s t test.

  • Fig. 4 Fire activity related to aridity.

    (A) Probability density function (%) for monthly precipitation to potential evapotranspiration ratio (P/PET) versus monthly regridded burned area (Kha) for each 0.5° × 0.5° grid in southeastern Siberia. The thick black line shows averaged burned area (Kha) in each P/PET bin. (B) Correlation coefficient map for averaged January to May P/PET with February to March 850-hPa geopotential height anomalies over southeastern Siberia. (C) Correlation coefficient map for total annual local burned area with January to May P/PET in each grid cell. Dotted area indicates significant region at the 90% confidence level based on Student’s t test.

  • Table 1 Correlation matrix between burned area and climatic variables.

    * and ** indicate significance at the 95 and 99% confidence level based on Student’s t test, respectively.

    JanuaryFebruaryMarchAprilMayJune
    Niño 3.40.130.140.130.110.060.10
    AO0.100.430.46*−0.070.16−0.08
    850-hPa geopotential height0.060.60**0.77**0.210.110.09
    Temperature0.080.410.54*0.46*−0.37−0.19
    Precipitation−0.18−0.40−0.32−0.27−0.14−0.08
    Potential evapotranspiration0.140.280.56**0.50*−0.08−0.11
  • Table 2 Soil moisture anomalies during high-temperature case (highest 5 years) and low-precipitation case (lowest 5 years) events depending on permafrost types.

    * indicates significance at the 95% confidence level based on the bootstrap method. In the bootstrap method, to get probabilistic density function, random resampling is repeated 10,000 times from the observed data.

    April soil moisture anomaly
    (m2 m−2)
    Continuous and
    discontinuous permafrost
    (>50%)
    Sporadic permafrost
    (10–50%)
    Isolated permafrost
    (0–10%)
    Nonpermafrost
    Composite of February to
    March high-temperature
    case
    −6.83 × 10−3 (P = 0.05*)−8.25 × 10−3 (P = 0.04*)−8.54 × 10−3 (P = 0.06)−3.27 × 10−3 (P = 0.19)
    Composite of February to
    March low-precipitation
    case
    −0.38 × 10−3 (P = 0.49)−4.53 × 10−3 (P = 0.16)−1.19 × 10−3 (P = 0.37)−0.39 × 10−3 (P = 0.45)

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/6/2/eaax3308/DC1

    Table S1. Correlation matrix between burned area and aerosol optical depth at 550 nm based on MISR.

    Fig. S1. Month of maximum of fire activity.

    Fig. S2. Temperature and precipitation climatology.

    Fig. S3. Interannual variability of fire activity.

    Fig. S4. Atmospheric circulation related to AO index.

    Fig. S5. Climate indices versus burned area over southeastern Siberia.

    Fig. S6. Snow cover variation related to AO.

    Fig. S7. Snow water equivalent variation related to fire activity over southeastern Siberia.

    Fig. S8. Fire activity–related snow-albedo feedback term.

    Fig. S9. Soil moisture anomalies related to 850-hPa geopotential height anomaly and AO index.

    Fig. S10. Snow cover trend.

    References (4044)

  • Supplementary Materials

    This PDF file includes:

    • Table S1. Correlation matrix between burned area and aerosol optical depth at 550 nm based on MISR.
    • Fig. S1. Month of maximum of fire activity.
    • Fig. S2. Temperature and precipitation climatology.
    • Fig. S3. Interannual variability of fire activity.
    • Fig. S4. Atmospheric circulation related to AO index.
    • Fig. S5. Climate indices versus burned area over southeastern Siberia.
    • Fig. S6. Snow cover variation related to AO.
    • Fig. S7. Snow water equivalent variation related to fire activity over southeastern Siberia.
    • Fig. S8. Fire activity–related snow-albedo feedback term.
    • Fig. S9. Soil moisture anomalies related to 850-hPa geopotential height anomaly and AO index.
    • Fig. S10. Snow cover trend.
    • References (4044)

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