Arctic fires re-emerging

Abstract

Underground smouldering fires resurfaced early in 2020, contributing to the unprecedented wildfires that tore through the Arctic this spring and summer. An international effort is needed to manage a changing fire regime in the vulnerable Arctic.Wildfires are not a novel phenomenon in the Arctic, however 2020's fire season began two months early and has been far more severe than usual. While increasing fire activity in Boreal forests to the south 1, 2 and an unusually warm winter in the Arctic 3 have led some to suggest that this uptick in wildfires was inevitable, there is still uncertainty about their source and their local and global impact. Here, we discuss how the wildfires in the Arctic are changing and how the input and expertise of local and Indigenous communities will be essential to determine whether this year is an anomaly or the beginning of a new fire regime. Early burning season.Wildland fire experts generally believe that extremely early season fires in the Arctic -before aboveground vegetation tends to be flammable -are caused by holdover or so-called "zombie fires". One of the most fascinating aspects of zombie fires is that they represent a continuation of a previous growing season's fire rather than a new ignition source, such as lightning or campfires. Zombie fires can smoulder in carbon-rich peat below the surface for months or years 4 , often only detectable through smoke released at the surface and can even occur through cold winter months despite heavy snowmelt 5 . These types of fires in general are poorly understood, including their impacts on fuels and emissions of greenhouse gases and aerosols to the atmosphere 6 . However, if these fires, their increasing prevalence and large burn areas or deep burning conditions drive substantial emissions, then this would represent a strong feedback in the Arctic fire regime that needs to be considered by Earth system models or simulations of global biomass burning.Fire in fire-resistant landscapes. Evidence from 2019 and 2020 suggests that extreme temperatures accompanied by drying are increasing the availability of surface fuels in the Arctic. New tundra vegetation types, including dwarf shrubs, sedges, grasses and mosses, as well as surface peats, are becoming vulnerable to burning and what we typically consider to be "fire resistant" ecosystems, such as tundra bogs, fens, and marshes are burning (Figure 1). While wildfires on permafrost in Boreal regions of Siberia are not uncommon 7 , 2020's fires are unusual in that more than 50% of the detected fires above 65°N occurred on permafrost with high ice content. Ice-rich permafrost is considered to contain the most carbon-rich soils in the Arctic 8 and burning can accelerate thaw and carbon emission rates 9 . Burning of ice-rich

Divergent shrub‐cover responses driven by climate, wildfire, and permafrost interactions in Arctic tundra ecosystems

“…Although the NOAT selected by our study is among the most flammable tundra ecosystems on earth, our current understanding of fire–shrub interaction remains limited by the inherent paucity of tundra fires in general (Chipman et al, 2015; Hu et al, 2015). This is especially true for ice‐rich, poorly drained lowlands where fire disturbance has been historically rare due to saturated soils interspersed with numerous lakes, ponds, bogs, and fens that strongly inhibit fire ignition and spread (Hu et al, 2015; McCarty et al, 2020). As a result, our findings based upon five upland fires and three lowland fires should be interpreted with caution considering limited spatial extent of historical tundra fires (AICC, 1943–2020) coupled with substantial spatial heterogeneity of tundra landscape (e.g., Hamilton, 2010; Pastick et al, 2015).…”

The Arctic Carbon Cycle and Its Response to Changing Climate

“…2019 was a severe fire year across Siberia and Alaska, with record-breaking heat, and fires may have continued to burn deep in peat soils over the cold season and break out again during the 2020 warm season. These holdover fires, also known as "zombie fires," have been observed in the Arctic in recent years and could accelerate permafrost loss and carbon emissions ( [58]; https:// phys.org/news/2020-05-scientists-zombie-arctic.html). Indeed, 2019 and 2020 both appear to be record-setting years for CO 2 emissions from fires north of the Arctic Circle (https://www.economist.com/graphic-detail/2020/09/07/thisyears-arctic-wildfires-are-the-worst-on-record-again, https:// phys.org/news/2020-09-co2-emissions-arctic-wildfires-eu.…”

Reviews & Syntheses: Arctic Fire Regimes and Emissions in the 21st Century

“…The Arctic Council's role as an agent of change in the region is promising, as it has moved its role from policy informing to policy making (Barry et al, 2020). Given the extreme fire season of 2020, an Arctic Council-led initiative for Pan-Arctic fire monitoring, prevention, and management is strongly needed for a rapidly changing Arctic (McCarty et al, 2020 Potentially expanding existing efforts or coordinating with new initiatives to incorporate the five other Indigenous permanent participants, as well as more efforts from the science and disaster response agencies of the eight member states and the expertise of other Arctic Council working groups, could create the type of community-and Arctic-centric science needed for Pan-Arctic fire policies and to increase the capacity for the Indigenous peoples of the Arctic to monitor and protect their Arctic homelands (Wilson, 2020)…”

“…Preliminary results by Scholten and Veraverbeke (2020), indicate that overwintering fires are more likely to be holdovers from high severity fires, emerging more frequently in lowland black spruce-dominated boreal forests. McCarty et al (2020) hypothesize that some of the earliest fires along still-frozen thermokarst lakes of Sahka Republic in May 2020 may be holdover fires, as the drivers and extent of early season human-caused ignitions are still not well-documented in the scientific literature for much of the Arctic.…”