Part of the Radiation Budget, pulled from the IPCC Fourth Assessment Report. Source: Kiehl and Trenberth (1997).

Carbon dioxide has a carbon cycle much like water has the water cycle. CO2 is emitted and absorbed in numerous ways. Whether it’s a chemical reaction in the atmosphere that changes molecules of CO2 into something else, the combustion of a fossil fuel producing CO2, or the oceans taking in CO2 from the air and depositing it deep under the surface, they all play roles as sources and sinks of atmospheric carbon dioxide.

Figure from ESRL Carbon Cycle Greenhouse Gases Group. The data comes from the Carbon Cycle Network that includes NOAA Baseline Observatories (like the South Pole Observatory) as well as cooperative programs around the world.

The figure above graphically depicts the carbon cycle on an annual basis. The red strip indicates the data that has been gathered over the last 10 years from the South Pole. The waves in the graph are from the seasonal uptake of carbon dioxide by plant life. For example, in the summertime when trees have their leaves, and plant life is not dormant, you see a large dip in CO2 values especially in the northern hemisphere because plants take in CO2 for photosynthesis. Also notice the difference in variation (waviness) of CO2 between the Northern Hemisphere and Southern Hemisphere. This is due to the very large forests in the N. Hemisphere compared to the S. Hemisphere, and the fact that the N. Hemisphere is more populated. Aside from the annual variation, notice the steady rise of CO2.

In previous posts, we’ve looked at some of the instruments at the Atmospheric Research Observatory (ARO) that measure things like solar radiation. At the South Pole, carbon dioxide has been measured for just over 50 years now and there are a few different methods of obtaining a CO2 value.

One of them is using our Portable Sampling Unit (PSU) that looks like a suitcase containing a pump inside. Using the PSU, we walk out into the Clean Air Sector (CAS), turn on the unit, and pump air into glass flasks which are then shipped back to the Earth Systems Research Laboratory in Boulder, CO for analyzing. (I shot a video of the process which can be seen here.)

The second is hooking the same type of glass flask that we use in the PSU to the Through Analyzer. What this does is bottle up a sample using the same sample lines as our third method uses a Non-Dispersive Infrared Detector (NIDR).

The Portable Sampling Unit (PSU). Flask samples with this unit are done once a week. On the first and fifteenth of the month, they are done in conjunction with sampling from the Through Analyzer.

Upper right: The Li-COR Non-Dispersive Infrared Analyzer. Lower Left: A display graphing the voltages recorded over the past four hours. The spikes are the calibration gases measured once every hour.

The NIDR uses an infrared source which is a heated filament that emits infrared radiation around the same wavelength that carbon dioxide likes to absorb (usually around 4.26 µm). This energy travels through two absorption cells, one of which is containing a sample of air from outside, and another that is containing a reference gas from a compressed gas cylinder. A mechanical chopper wheel then alternates between the sample and reference gas measuring the difference in the amount of absorption between the two. Using the difference of the two cells helps negate the problem of changes in temperature and pressure. Changes in pressure and temperature change the density of the sample which would skew the amount of carbon dioxide molecules in the measurement. This is a very useful machine that requires very little maintenance and gives us measurements continuously 24 hours a day, 7 days a week (there is about 15 min of each hour that it measures accurate known amounts of carbon dioxide in other gas cylinders for calibration).

On the right are the three calibration gases and the reference gas.

Here is a comparison of when the winds are in the Clean Air Sector (CAS), and when they are blowing station air towards the Atmospheric Research Observatory (ARO). The this graph is when the winds were from the direction of the station and the graph that follows is when the winds are in the CAS.

As you can see we easily pick up local carbon dioxide when the winds are blowing from the station. Winds at ARO are within the CAS probably greater than 90 or 95 percent of the time which is why it is such a good place to get long term continuous measurements of CO2.

Chief Scientist Ken Taylor and science tech Anais Orsi looking at layers in backlit snowpit.

A one-meter long piece of ice core illuminated with a light. The green netting on the core is used to help hold the ice together in case it spontaneously fractures.

The bubbles visible in this piece from an Antarctic ice core sample contain carbon dioxide and other gases that were trapped in the ice when formed thousands of years ago. Researchers carefully crush the piece and capture the gases that escape when the bubbles break. This allows them to better understand what carbon dioxide levels were over time.

Heidi Roop, a science technician, worked with more than 100 scientists to recover a 2-mile-long (3.5-km-long) ice core from the West Antarctica Ice Sheet (WAIS) Divide. Imagine, that’s a column of ice twice as tall as the Grand Canyon is deep! The properties of each layer of an ice core reveal a slice of climate history. The WAIS team estimates that this ice core will reveal climate changes that have happened as far back as 100,000 years, a time when woolly mammoths still walked the earth.

During the 2009–2010 season, Heidi helped the WAIS team uncover new chapters of the climate story by drilling deeper into the ice. The WAIS scientists were able to decipher the climate year by year back approximately 40,000 years and at decadal (10-year) resolution from 40,000 to 100,000 years, making it the most detailed ice core record ever collected in the Southern Hemisphere. With the ability to extract annual (1-year) to decadal climate information such as past greenhouse gas concentrations, the climate record developed from WAIS can be directly related to ice cores from Greenland. By comparing records from the Southern and Northern hemispheres, our understanding of global climate change will be more complete. The earth’s climate history will be known in more detail than ever before—and it’s bound to be an interesting story!

Early drill and recovery attempts of the buried glacier ice.

Sediment lenses cross cutting through a 30 cm ice core.

The outstanding question is how old is the ice? Ash deposits overlying the ice are dated to as old as 8.1 Ma (million years ago) which would make the underlying glacier the oldest ice yet discovered on our planet. To further convince skeptics that the ice is indeed old, the principal investigators of the grant (David Marchant, Boston University, and Michael Bender, Princeton University) are attempting to date the age of the ice directly.

An in-situ ash wedge in debris overlying buried ice. The wedge is approximately 30 cm across and 40 cm tall. Such deposits can be dated to give a minimum age for the overlying glacial debris.

To understand how this is done we need to go back to when the planet was forming 4.6 billion years ago. Since the formation of the earth, there has been a slow release of gas from the interior of the planet to the atmosphere (i.e. degassing via volcanic activity). One gas in particular is an isotope of Argon. This isotope does not decay thus its concentration is slowly building up in the earth’s atmosphere over time. Atmospheric gas trapped in old ice would have less Argon isotope compared to recently formed glacier ice. The principal investigators will use this technique to analyze the gases trapped within the glacier ice we collect during this field season and determine an age of the ice. If indeed it is the oldest ice yet found on earth, we will have the opportunity to directly measure important greenhouse gases such as CO2 at timescale millions of years back into earth’s history.

The Ceremonial South Pole

NOAA’s Atmospheric Research Observatory

NOAA’s Atmospheric Research Observatory (ARO) at the South Pole is part of a network of stations around the world that monitor properties of the earth’s atmosphere. This station is part of NOAA’s Earth Systems Research Laboratory (ESRL), Global Monitoring Division (GMD) located in Boulder, CO. Some of the items that GMD monitors are aerosols, radiation, carbon cycle gases (CO₂), ozone and water vapor, as well as halocarbons and other trace gases. NOAA has been maintaining some of these measurements, including tracking the increasing concentration of carbon dioxide in the atmopshere, dating back to the International Geophysical year of 1957 giving more than 50 years of continuous data.

The Amundsen-Scott South Pole Station

Long term data is extremely useful when studying the earth’s climate. Due to climate’s high variability, it is necessary to have a long set of continuous data to pick out trends and to help predict the state of the atmosphere in the future. Because it is in such a remote location, far from any source of emissions or human activities, the ARO gives scientists a baseline level of the global average measurements. Air at the South Pole is the “cleanest on earth,” free of local influences from humans such as factories and cars, as well as natural effects from things like volcanoes.

Permafrost gone soft

“Not only has climate change begun, but we are seeing a significant impact,” said Wayne Pollard from McGill University in Montreal, Canada in his plenary talk on “The effects of climate change on polar landscapes.” His talked focused on the Arctic permafrost, which refers to ground that has remained frozen for a minimum of 2 years and as many as several thousands of years. More than 25% of the Earth’s land surface is considered permafrost, comprising 50% of Canada, 80% of Alaska, and 60% of Russia. Pollard reported that permafrost regions are one of the most sensitive and severely affected by climate change. He further stated, “40-60% of the permafrost could disappear in the next 100 years.”

Melting permafrost from above.

The melting permafrost causes a host of problems for local Arctic populations and the environment. As a solid landmass, permafrost provides stability to Arctic slopes. In contrast, “when the permafrost melts, it turns into a slurry of liquefied mud, referred to as a thermokarst. The result is thaw lakes and tundra ponds and frozen peat turning into vast wetlands,” says Pollard. Thawing permafrost combined with reduced sea-ice and increased storm activity will collectively increase the erosion of Arctic coastlines, directly impacting coastal communities, culturally important sites and industrial facilities.

In Shishmaref, Alaska, melting permafrost has contributed to major erosion, forcing residents to consider moving the entire village to a new location.

Most alarming is the global effects of melting permafrost. Scientists have reported that Arctic soils hold 30 percent or more of all the carbon stored in soils worldwide. When it is frozen, the permafrost acts as a sink for carbon dioxide and methane, two of the major greenhouse gases. Pollard explained that now as it melts, it will become a source. Since the conference, even more alarming results have been reported. Edward A.G. Schuur of the University of Florida and an international group of coauthors has shown that the melting permafrost is a far larger source for greenhouse gases than previously believed and will indeed further contribute to global warming. See the September, 2008 press release at
http://www.aibs.org/bioscience-press-releases/080828_thawing_permafrost_likely_to_boost_global_warming.html

The summer tundra.

Carbon dioxide is a colorless, odorless gas that makes up .04 percent of the earth’s atmosphere. It’s released by the breakdown of organic materials, by animals when they respire, and by the burning of fossil fuels. Carbon dioxide isn’t toxic—after all, we exhale it with every breath and use it to make our drinks fizzy. However, carbon dioxide is considered a pollutant because, as a greenhouse (heat-trapping) gas, it’s a significant contributor to global warming.

Factory pollution is but one of the ways industrial society has contributed to climate change.

In the last 150 years, carbon dioxide from factories, power plants, and fuel-burning vehicles has boosted natural levels of carbon dioxide in the atmosphere. Data from ice cores taken in Antarctica show that carbon dioxide in our atmosphere has increased 36 percent from preindustrial levels. Carbon dioxide raises global temperature by trapping heat that would otherwise escape directly into space.

Continually climbing levels of carbon dioxide are of special concern at the poles for two reasons. First, polar regions are especially sensitive to global warming. Already, temperature increases measured at the poles are twice those measured at the equator. (See Climate Change.) Also, warming temperatures in the Arctic may release even more carbon dioxide and other greenhouse gases such as methane, by melting frozen soil called permafrost. (See Tundra and Permafrost.) In this way, thawing at the poles may result in a positive feedback loop, in which thawing causes faster warming, in turn causing more thawing.

The Atmospheric Research Observatory at the South Pole is part of a world-wide campaign by NOAA (the National Oceanic and Atmospheric Administration) to collect long-term measurements on compounds in the atmosphere. In addition to this South Pole station, NOAA maintains climate observatories in Samoa, Mauna Loa, Hawaii, and Barrow, Alaska.

Predicting the outcome of effects such as thawing of permafrost requires a thorough understanding of the carbon cycle, a collection of processes whereby carbon (in various forms) shifts between the atmosphere, the ocean, the land, and living things. The carbon cycle is complex, however, and not yet fully understood in a warming world.

To keep track of carbon dioxide and study global warming, scientists use gas detectors to continually monitor global atmospheric carbon dioxide levels. Measurements must be made far from sources that might skew the reading, so the monitoring stations are located in remote locations, including the South Pole and Barrow, Alaska. In time, these measurements may help scientists better understand the carbon cycle and predict future climate change.

Steve Hastings on the tundra.

Performing controlled scientific experiments in a living ecosystem is complex and very difficult, but important to understanding how biological communities will respond to and affect climate change. This is an especially critical research question in the high Arctic, where global warming is happening at twice the rate of more temperate regions of the earth.
Steve Hastings and his colleagues (Principal Investigators Drs. Oechel, Tweedie, Oberbauer, and Gamon) are looking at how soil moisture, expected to change with a changing climate, might in turn affect the release or retention of greenhouse gases such as carbon dioxide and methane.

The project site.

The interdisciplinary team’s large-scale project will manipulate the water moisture in soil within different sections of a small, shallow lake that is less than 1 foot deep (30 cm), 1,000 yards x 300 yards (915 m x 27 m). Lakes such as this dot the landscape on the North Slope of the Alaskan Arctic, making up 50–75 percent of the aerial coverage. In the experiment, each section of the lake will be separated by a plastic sheet that will act as a dam. One portion of the lake will serve as an experimental control while another will be flooded so that the water table is adjusted a foot above that of the control. Another section will be drained so that the water table is a foot below the control. Comparing these three regions will help Steve and his colleagues understand how soil moisture affects the release of greenhouse gases.

A view of the tundra from the field.

While climate models presage a wetter, warmer atmosphere, higher temperatures in the Arctic could result in more evaporation and drier soils. Drier conditions are predicted to result in more carbon dioxide release but less methane emissions. Wetter soil conditions would likely result in more methane release but less carbon dioxide release. The balance between these two greenhouse gases is important to know because methane is 20 times more efficient at trapping warmth than carbon dioxide.

The field lab.

The long-term goals of the project are to quantify the type and amount of greenhouse gases that would be released in either a wetter or drier Arctic climate. But there may be other climate change impacts on the tundra. As temperature and moisture fluctuates, plant biomass (the amount of green matter) as well as plant types could also change. As soil moisture changes, the nutrients available to plants will also likely change, but scientists don’t yet know how nutrient balance will be affected. All of these factors (soil nutrients, plant type, and plant biomass) will be affected by changes in soil moisture and can ultimately modify the amount and types of greenhouse gases released by the tundra. This could tip the climate balance not just in the Arctic, but throughout the world. With almost 20 percent of the world’s soil organic carbon stored (for now) in the frozen layers of the Arctic called permafrost, a changing climate has the potential to intensify the atmospheric rise in greenhouse gases and contribute to global warming. Conversely, with changes in plant type, and possibly more nutrients, plants could grow bigger and help soak up greater quantities of atmospheric carbon dioxide. Plant physiologists, hydrologists, geographers, microbiologists, and climate modelers are working together to collect and interpret this large-scale manipulation experiment designed to give us insight into the future climate on earth.

Inside the lab.