Fire regimes during the Last Glacial

Abstract

Sedimentary charcoal records document changes in fire regime. We have identified 67 sites (30 sites with better-than millennial-resolution) which have records for some part of the last glacial to analyse changes in global fire regimes. Fire was consistently lower during the glacial than during the Eemian and Holocene. Within the glacial, Marine Isotope Stage (MIS) 3 is characterised globally by more fire than MIS 2. The signal for MIS 4 is less clear: there is more fire in the northern hemisphere and less fire in the southern hemisphere than during MIS 2 and 3. The records, most particularly records from the northern extratropics, show millennial-scale variability in fire regimes corresponding to the rapid climate changes associated with Dansgaard-Oeschger (D-O) cycles. Most of the D-O cycles during the last glacial and all of the Heinrich Stadials are apparent in the composite global record of the high-resolution sites: fire increases during D-O warming events and decreases during intervals of rapid cooling. Our analyses show that fire regimes show a lagged response to rapid climate changes of ca 100-200 years in the case of D-O warming events, ca 0-100 years in the case of D-O cooling events and ca 200 years in the case of Heinrich Stadials. The strong climatic variability experienced during the glacial resulted in important changes in fire regimes even though the base level of biomass burning was less than today.

Limited response of peatland CH<sub>4</sub> emissions to abrupt Atlantic Ocean circulation changes in glacial climates

“…Whilst records of charcoal suggest a dynamic relationship between climate and biomass burning (Daniau et al, 2010), ice-core isotopic evidence appears to argue against substantial contributions on either the glacial-interglacial or abrupt timescales (Möller et al, 2013). For the abrupt CH 4 rise at the end of the Younger Dryas, Melton et al (2012) inferred a strong contribution from biomass burning and thaw lakes.…”

Terrestrial biogeochemical feedbacks in the climate system

“…On centennial to millennial timescales, fire activity covaries with climate change 79 -indeed, biomass burning declined towards the Little Ice Age -supporting the interpretation by Ferretti et al 80 of the icecore record of changes in 13 CH 4 as a reflection of changes in biomass burning. Fire regimes show a large response to both rapid warming and rapid cooling 81,82 ; during the last glacial period, for example, fire regimes tracked Dansgaard-Oeschger warming events with lag times on the order of a few decades (Fig. 2); the lag in response to the cooling associated with Heinrich stadials was slightly longer 81 .…”

“…Fire regimes show a large response to both rapid warming and rapid cooling 81,82 ; during the last glacial period, for example, fire regimes tracked Dansgaard-Oeschger warming events with lag times on the order of a few decades (Fig. 2); the lag in response to the cooling associated with Heinrich stadials was slightly longer 81 .…”

Abrupt climate and vegetation variability of eastern Anatolia during the last glacial

“…3d). During stadials, lower microscopic charcoal concentrations (between 300 and 850 particles cm −3 ) characterizes an open dry desert-steppe landscape with low vegetation density (e.g., MIS 5b; Daniau et al, 2010;Sadori et al, 2015;Vanniere et al, 2011;Fig. 3d).…”