August 5, 2011

Arctic Fires and CO2 Emissions

Filed under: Arctic, Polar

Last week, a widely-repeated pronouncement was made, that after an absence of more than 10,000 years, “wildfires have returned to the Arctic tundra” spurred by an apparent increase in lightning strikes and leading to carbon dioxide (CO2) releases from a traditional CO2 sink region. Another positive feedback to anthropogenic global warming. Oh yeah, and the fires will get worse and more widespread in the future.

But as with most dire global warming predictions, this one seems to lack grounding in reality.

This grave assessment of things arctic was issued by Michelle Mack (University of Florida) and co-authors after publishing in Nature magazine the results of their examination of the impacts of a large wildfire which in 2007 burned about 400 square miles of Alaskan tundra in the Anaktuvuk River basin and was reported to be the “biggest wildfire ever recorded on the North Slope of Alaska.”

Lead author Michelle Mack described her main findings in an interview with NPR’s Christopher Joyce:

Ms. MICHELLE MACK (Ecologist, University of Florida): I’m at Toolik Lake field station, in a trailer that’s on a gravel pad that’s in the middle of Arctic tundra.

JOYCE: Mack is an ecologist from the University of Florida who prefers the desolate beauty of the North Slope of Alaska and the snowcapped Brooks Mountain Range. She says what the Anaktuvuk fire did—burn through 400 square miles of tundra—amazed her.

Ms. MACK: We’ve never seen anything like it in this area. What’s surprising is that forests have huge trees, whereas tundra has six-inch tall, tiny little plants.

JOYCE: Nonetheless, the fire sizzled for three months, then burst into a major conflagration before snowfall put it out. So if there weren’t any trees, what was there to burn?

Ms. MACK: It’s coming from the soil.

JOYCE: Organic matter, dead plants, accumulated over decades. And what set it off was dry weather, and then a lightning strike.

Ms. MACK: There’s been a marked increase in lightning strike activity on the North Slope, particularly in the last 10 years.

JOYCE: But Mack was really surprised when she calculated how much carbon that fire put up into the atmosphere. It was two million tons. Is that a lot? Well, think of it this way: Every year, the Arctic tundra absorbs more carbon from the atmosphere than it releases. It’s a net carbon sink. Because carbon warms the atmosphere, the Arctic is actually cooling the planet by taking up carbon. But Mack says the Anaktuvuk fire reversed that equation.

Ms. MACK: One fire, that alone is enough to offset the whole uptake.

JOYCE: That’s right. The fire put out more carbon than the entire Arctic tundra absorbed in 2007. That includes Alaska, Canada, Greenland and Russia.

Mack’s findings are part of an increasingly feverish research effort going on in the Arctic. Arctic sea ice has been melting, putting more moisture in the air and creating more thunderstorms.

Let’s look at a few of these claims and their significance to “global warming.”

Thunderstorms in the arctic, including northern Alaska, were reported by the region’s earliest explorers.

A brief article by T. Neil Davis, from the University of Alaska titled “Arctic Thunderstorms” and published in 1979 included this account:

Looking into thunderstorm history, Mr. Arne Hanson of the Naval Arctic Research Laboratory at Barrow, Alaska, has uncovered an observation of an arctic thunderstorm made in 1580. A manuscript Hanson has prepared contains a quotation written aboard a ship sailing the Kara Sea, north of Siberia: “… the wince with a showre and thunder came to the Southwest and then wee ranne East Northeast.”

Several thunderstorms on the north Siberia coast were recorded in the late 1700’s, and at least nine were observed on the northern coasts of Canada, Alaska or Siberia by explorers in the period 1815-1826.

And where there’s thunderstorms there’s fire.

The occurrence of wildfires in the region of northern Alaska has been summarized since the early 1950s. For instance, Racine et al. (1985), reviewed wildfire records from 1956 through 1983 for the Noatak River watershed region which lies to the west of the North Slope and reported 79 fires during the 28-year study interval, the biggest of which burned nearly 200 square miles of “treeless thaw lake-studded portion of the Mission Lowlands tundra” and most, if not all of which were started by lighting.

And while the frequency of fire occurrence the region of Alaska’s North Slope where the 2007 Anaktuvuk River fire took place is less than in the region studied by Racine et al., fires on the North Slope are not undocumented.

Consider the USDA Forest Service Research Note “Wildfires and Thunderstorms on Alaska’s North Slopes” written in 1973 by Richard Barney and Albert Comiskey, which has the following conclusion:

Although there has been limited formal record of fire previous to this time [1971], we think it is safe to assume that lightning and the associated weather and fuel conditions suitable for fire have been present for many years. It also seems reasonable to assume that fires have not just recently begun occurring north of the Brooks Range. With continued activity in that location, we are certain to receive more and more wildfire reports. Although the North Slope is apparently not a fire-dominated ecosystem, wildfire is not unknown to this arctic environment.

So there is historical documentation of both thunderstorms and wildfires in the Arctic including Alaska’s North Slope for many years into the past—and clearly previous to the past decade—facts which serve to destroy both the lead-in of the University of Florida press release announcing the findings of Mack et al. (“After a 10,000-year absence, wildfires have returned to the Arctic tundra…”) as well as NPR’s implication that the 2007 fire was a result of thunderstorms spawned by reduced sea ice caused by anthropogenic global warming.

Our Figure 1 shows why the latter claim is unsubstantiated. Figure 1 shows the sea ice conditions for the Arctic since 1900.


Figure 1. Arctic sea ice extent (data source: Cryosphere Today)

Now, whether or not you believe the details of this Arctic sea ice history as you go back in time (see here for problems with this history ), the point is that there was a lot more sea ice during the summers back in the early 1970s and years prior, than there was in 2007—the year of the fire, which NPR’s Christopher Joyce desperately tried to link to sea ice decline: “Mack’s findings are part of an increasingly feverish research effort going on in the Arctic. Arctic sea ice has been melting, putting more moisture in the air and creating more thunderstorms.” History tells a different story—that even with high sea ice conditions, thunderstorms can and do develop over the North Slope of Alaska and spark wildfires.

And what about claims that CO2 emissions from arctic wildfires will offset the carbon storage produced by a greening arctic and increase the rate of global warming?

That, too, is a bit of a stretch.

Figure 2 below shows the weekly progression of the concentration of atmospheric carbon dioxide as measured at Mauna Loa observing station during the period January 2000 through July 2011. Since CO2 is generally well-mixed in the atmosphere, Mauna Loa’s measurements should reflect anything unusual that is going on in the annual CO2 cycle. The period of the time when the 2007 Anaktuvuk River fire was burning is highlighted.

Stare at/ponder/analyze Figure 2 all you want, but nothing unusual is going to pop out either during or immediately following the Anaktuvuk River fire. Simply put, the CO2 released by the “biggest wildfire ever recorded on the North Slope of Alaska” had an undetectable impact on the evolution of the global CO2 concentration.


Figure 2. Weekly atmospheric concentration of carbon dioxide as measured at Mauna Loa, January 2000 through July 2011 (data source: http://www.esrl.noaa.gov/gmd/ccgg/trends/mlo.html)

The bottom line is that undoubtedly Mack and co-authors have done a lot of hard field work documenting the details of the large 2007 Anaktuvuk River fire and collecting valuable data on fire characteristics and their impacts on the local tundra environment of Alaska’s North Slope. However, they have overreached in concluding that such fires either are caused by, or feedback from factors that extend much beyond that local environment. The paper would have been better off, and more scientifically grounded, had it not brought global warming into the discussion—although, in that case, it would not have found publication in Nature or press coverage the world over.

References:

Barney, R.J., and A.L. Comiskey, 1973, Wildfires and thunderstorms on Alaska’s north slopes. USDA Forest Service Pacific Northwest Forest and Range Experiment Station, Portland, OR. Research Note PNW-311. 8 p.

Davis, T.N., 1979. Arctic Thunderstorms. Article #325, Alaska Science Forum, Geophysical Institute, University of Alaska Fairbanks, http://www2.gi.alaska.edu/ScienceForum/ASF3/325.html.

Mack, M., et al., 2011. Carbon loss from an unprecedented Arctic tundra wildfire. Nature, doi:10.1038/nature10283.

Racine, C.H., J.G. Dennis, and W.A. Patterson III, 1985. Tundra fire regimes in the Noatak River Watershed, Alaska: 1956-83. Arctic, 38, 194-200.




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