Abstract
The mid-Pliocene is a valuable time interval for
investigating equilibrium climate at current atmospheric CO2
concentrations because atmospheric CO2 concentrations are
thought to have been comparable to the current day and yet
the climate and distribution of ecosystems were quite different. One intriguing, but not fully understood, feature of the
early to mid-Pliocene climate is the amplified Arctic temperature response and its impact on Arctic ecosystems. Only
the most recent models appear to correctly estimate the degree of warming in the Pliocene Arctic and validation of the
currently proposed feedbacks is limited by scarce terrestrial
records of climate and environment. Here we reconstruct the
summer temperature and fire regime from a subfossil fenpeat deposit on west–central Ellesmere Island, Canada, that
has been chronologically constrained using cosmogenic nuclide burial dating to 3.9 + 1.5/ − 0.5 Ma.
The estimate for average mean summer temperature is
15.4 ± 0.8
◦C using specific bacterial membrane lipids, i.e.,
branched glycerol dialkyl glycerol tetraethers. This is above
the proposed threshold that predicts a substantial increase in
wildfire in the modern high latitudes. Macro-charcoal was
present in all samples from this Pliocene section with notably higher charcoal concentration in the upper part of the
sequence. This change in charcoal was synchronous with a
change in vegetation that included an increase in abundance
of fire-promoting Pinus and Picea. Paleo-vegetation reconstructions are consistent with warm summer temperatures,
relatively low summer precipitation and an incidence of fire
comparable to fire-adapted boreal forests of North America
and central Siberia.
To our knowledge, this site provides the northernmost evidence of fire during the Pliocene. It suggests that ecosystem
productivity was greater than in the present day, providing
fuel for wildfires, and that the climate was conducive to the
ignition of fire during this period. The results reveal that interactions between paleo-vegetation and paleoclimate were
mediated by fire in the High Arctic during the Pliocene, even
though CO2 concentrations were similar to modern values.
investigating equilibrium climate at current atmospheric CO2
concentrations because atmospheric CO2 concentrations are
thought to have been comparable to the current day and yet
the climate and distribution of ecosystems were quite different. One intriguing, but not fully understood, feature of the
early to mid-Pliocene climate is the amplified Arctic temperature response and its impact on Arctic ecosystems. Only
the most recent models appear to correctly estimate the degree of warming in the Pliocene Arctic and validation of the
currently proposed feedbacks is limited by scarce terrestrial
records of climate and environment. Here we reconstruct the
summer temperature and fire regime from a subfossil fenpeat deposit on west–central Ellesmere Island, Canada, that
has been chronologically constrained using cosmogenic nuclide burial dating to 3.9 + 1.5/ − 0.5 Ma.
The estimate for average mean summer temperature is
15.4 ± 0.8
◦C using specific bacterial membrane lipids, i.e.,
branched glycerol dialkyl glycerol tetraethers. This is above
the proposed threshold that predicts a substantial increase in
wildfire in the modern high latitudes. Macro-charcoal was
present in all samples from this Pliocene section with notably higher charcoal concentration in the upper part of the
sequence. This change in charcoal was synchronous with a
change in vegetation that included an increase in abundance
of fire-promoting Pinus and Picea. Paleo-vegetation reconstructions are consistent with warm summer temperatures,
relatively low summer precipitation and an incidence of fire
comparable to fire-adapted boreal forests of North America
and central Siberia.
To our knowledge, this site provides the northernmost evidence of fire during the Pliocene. It suggests that ecosystem
productivity was greater than in the present day, providing
fuel for wildfires, and that the climate was conducive to the
ignition of fire during this period. The results reveal that interactions between paleo-vegetation and paleoclimate were
mediated by fire in the High Arctic during the Pliocene, even
though CO2 concentrations were similar to modern values.
| Original language | English |
|---|---|
| Pages (from-to) | 1063-1081 |
| Journal | Climate of the Past |
| Volume | 15 |
| DOIs | |
| Publication status | Published - 19 Jun 2019 |
