Multidecadal climate variability and climate interactions affect subalpine fire occurrence, western Colorado (USA)

Area of Science:

• Climatology
• Forest Ecology
• Paleoclimatology

Background:

• Subalpine forest fires are influenced by climatic variability.
• Understanding these influences is crucial for predicting future fire regimes.

Purpose of the Study:

• To investigate the relationship between climatic variability and subalpine forest fire occurrence in western Colorado from AD 1600-2003.
• To examine the role of major climate oscillations (ENSO, PDO, AMO) and their phase interactions on fire frequency.

Main Methods:

• Analysis of historical fire occurrence data (AD 1600-2003).
• Correlation analysis between fire data and climate indices: El Niño Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO).
• Examination of interannual and multidecadal relationships, including phase interactions.

Main Results:

• Fires occurred during negative ENSO/PDO phases and positive AMO phases, often linked to drought.
• Longer-term fire synchrony observed with cool PDO phases (20-year) and warm AMO phases (80-year).
• Combined warm AMO and cool ENSO/PDO phases ('triple whammies') significantly increased drought-induced fires.

Conclusions:

• The study suggests a potential shift to a different fire regime due to the recent transition to a warm AMO phase.
• Warm AMO phases, particularly with cool ENSO/PDO, promote higher fire frequencies in subalpine forests.
• Multidecadal climate oscillations play a significant role in modulating regional fire occurrence.