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

Aerosols have different properties depending on what they are made of. Some of those properties that are important are roughness, color, and size. These properties affect what happens to solar radiation as it reacts with the particle such as whether it will scatter or absorb. For example, a particle of black carbon (left over after burning of a fossil fuel let’s say) is going to be much more effective at absorbing solar radiation than a piece of salt that has a much lighter color as well as a shinier surface (shiner, brighter surfaces reflect radiation better). It is also important how they are distributed spatially around the globe and how long they stay in the atmosphere. To think more about the spatial distribution, at the South Pole, we have no vegetation, dirt, salt water, or large sources of combustion anywhere close to us (aside from our own station which is downwind from where we sample). We have extremely low concentrations of aerosols in the air here compared to a sand desert or near a volcanic eruption. The time that they spend in the atmosphere can depend on many things. If it is a large particle, it may settle back to the surface quicker. If it rains, the aerosol may get collected by the raindrops and land back on the surface. Depending on the hygroscopic (the ability for a surface to become wetted or have water stick to it) properties of the aerosol, water can also condense on them to make cloud droplets.

Speaking of cloud droplets, aerosols can indirectly affect solar radiation by being an ingredient for clouds to form. Water likes particular sizes and types of aerosols to condense upon. The name this particular type are Cloud Condensation Nuclei. If there are no Cloud Condensation Nuclei present, the water has nothing to condense onto and there will be no cloud. The size and type of aerosol affect the physical properties of the cloud as well. Therefore a change of aerosols in a region can change the type of cloud, thus changing its radiative properties. This dependency on Condensation Nuclei brings up yet another complicated variable that can affect the radiation budget.

So that explains a little bit why we are so interested about the “dust” in the air. Aerosols have a significant influence on climate processes. Now let’s take a look at the instruments that deal with aerosols at the South Pole.

The Condensation Nucleus Counter (CNC) does basically what its name says. It uses butyl alcohol to create a cloud by cooling the flow of the air through the instrument. Inside is a particle counter that counts how many droplets there are.

The Nephelometer measures the radiation scattering ability of the aerosols. By running air through the instrument and shining a light through the air, we can detect how much of that light is getting scattered with a photomultiplier tube (PMT). There are filters in front of the PMT in order to detect several specific wavelengths of light. If we know the output of light initially, and subtract what is detected, then we know how much light is scattered by the aerosols.

The Aethalometer is an instrument that we use to measure radiation absorbing aerosols. For this instrument, air is passed through a filter where the aerosols will deposit onto. The filter is illuminated by a lamp and there are two photocells that sense the light. One is a reference sensor on a spot of the filter with no aerosols, and the other is sensing where the aerosols where deposited. The difference between these 2 sensors is the amount of light absorbed.

Here I am using the Pollack which is an older instrument that is used to compare to the CNC. It creates a cloud by depressurizing a chamber which causes the air to cool and form a cloud. There is a PMT that detects light and I watch an ammeter to see how much the current goes down when the cloud forms.

Not pictured is the Water-Based Condensation Particle Counter which is very similar to the Condensation Nuclei Counter that is shown above. The laser inside broke during the summer and we were not able to send it to the lab, get it fixed, and get it back to the Pole before station closing.

So that is how we measure aerosol concentrations and their scattering/absorbing properties at the South Pole. The next process that we measure at the South Pole will be the Carbon Cycle and Greenhouse Gas (CCGG) group. We’ll take a look at the CO2 analyzer and the role that greenhouse gases play in the climate.

The Final Flight: February 14th, at 2:30am New Zealand time.

We have just barely over two weeks until the sun sets and temperatures are already starting to drop quickly. The day of station closing, temperatures were around -40F. Today it is the coldest since I’ve been here at -63F, and tomorrow it’s suppose to bottom out at almost -70F. It’s amazing how quickly it drops when that sun gets low. The cold temperatures also make everyday things difficult to deal with. We had an emergency response drill today that took place outside and I volunteer on the fire team. You have to be really conscious about your gear because the SCBA (Self Contained Breathing Apparatus) hoses start to freeze and can crack easily. A fire fighter isn’t much good without a working SCBA. Frostbite is a big concern as well. The fire gear gloves and boots are not insulated for cold and do a very poor job of keeping your fingers and toes warm.

South Pole Station from ARO.

As for the science here at ARO (Atmospheric Research Observatory), not too much has changed. I’m still coming out here every day to check to make sure everything us running as it should be and taking air samples in flasks every week. One thing that is starting to change is our ability to do Dobson observations. The Dobson Spectrophotometer is an instrument that uses sunlight to measure total column ozone in the atmosphere. When the sun is this low on the horizon, there is a lot of stray refracted light that affects the measurements and can give us bad results. You may ask, “How do you take measurements in the winter?” Well this is done by using the reflected sunlight off of the moon. So we are able to take sporadic observations to coincide with our balloon flights through the winter. The solar radiation instruments on the roof will be coming down soon after sunset as well, which will be a small project for us. Here is a brief description of the solar radiation measurements we have at ARO and why we are measuring it.

Incoming solar radiation is the backbone of what drives our climate. Changes in the amount of radiation reaching the earth from the sun can be the difference between being in an ice age or not. It is important for us to know how much radiation is a) reaching the surface, b) what type of radiation it is (wavelength), and c) how much is bouncing back off the surface. This is what’s called the “Radiation Budget” in its most basic form. The “Radiation Budget” involves many other processes but the pictures and descriptions below show how we break down the “Radiation Budget” into its basic components at ARO.

The Solar Tracking NIP (Normal Incidence Pyroheliometer)

The NIP tracks the sun in all 360 degrees. It measures direct incoming solar radiation of specific wavelengths.

Diffuse Pyranometer

The diffuse pyranometer blocks out the incoming direct solar radiation and measures any radiation that is getting reflected and refracted from substances in the atmosphere (or any radiation taking an indirect path to the surface).

Pyranometers

These pyranometers detect all incoming solar radiation both direct and indirect. The two outer ones have filters on them to divide it up into shortwave (UV) and longwave (infrared) radiation.

Albedo Instruments

The “Albedo Rack” is basically exactly the same as the pyranometers except that they are turned upside down. They then measure the amount of solar radiation that is reflected off of the earth’s surface. Roughness and color play a role in Albedo meaning that a smooth surface is going to reflect more than a rough surface, and a white surface is going to reflect more than a black surface.. Therefore, it is important not to disturb the snow under these instruments because we want the natural state of the surface. In addition to reflected radiation, it monitors infrared radiation emitted by the earth.

A more complex version of the “Radiation Budget” or “Energy Balance” pulled from the IPCC Fourth Assessment Report.

As you can see, in the above figure, there is a lot that really goes into the “Radiation Budget” and it is a very complex system. When the solar energy comes into the atmosphere, it can take a variety of paths. It can get interrupted by clouds, gases, aerosols and other substances. Two of these processes in the system we observe at ARO as well such as Aerosols, and Greenhouse Gases which I will talk about in a later post.

Hopefully this explains a little bit what’s behind the solar radiation observations that we take at ARO. The South Pole and Mauna Loa have the longest continuous running solar radiation observations of this kind. It’s extremely important that we understand what happens to solar radiation as it passes through the atmosphere and hits the earth’s surface if we want to gain a good understanding of how earth’s climate works. It is even more important as we try to predict future climates.

ABOARD THE JOIDES RESOLUTION, IN TRANSIT TO HOBART, TASMANIA– The work of the ship ended as quickly as it started nearly two months ago. We finished drilling Site 1361 and logged the hole. The drillers tripped 3500 meters of pipe and prepped it for storage as the ship will not drill again until July – off the coast of British Columbia. Everyone on board is absolutely brain dead from the non-stop grind of 12-hour shifts day after day. But all are happy as well. We’ve completed most of our objectives and made some exciting discoveries. When we did not meet with complete success it was always because of weather and ice, either encroaching sea ice or fields of icebergs so thick that we had no chance to pass.

Relaxing with some music after the work is done.

Now we have some days in transit. These days are filled with meetings to design our post-cruise research. We will all spend much more time at home working on the cores than our actual days at sea on this expedition. Some of the methods we will employ are expensive and difficult and we have recovered nearly 2000 meters of core. This means that we must carefully select the intervals we will study, so that we can answer the most important questions about Antarctic climate change as quickly as we can. For some of us, the analytical work will extend over the next 4 years. Then other scientists will work on these cores for decades to come. They will be stored in a vast library of ocean cores in College Station, Texas, at the IODP core repository where they are available to scientists from all over the world.

What I like most about these days in transit is going off shift. I no longer set my alarm to awake at 11PM. The two shifts mingle at meals and in the labs, almost as strangers at first as they have not seen much of each other for more than 7 weeks.

The whole team for Expedition 318. Photo courtesy of John Beck, IODP.

Working groups between the shifts assemble to design research strategies and timetables. I will lead a group that will make oxygen isotopic measurements of the small shells of amoeba-like organisms called foraminifera. Forams, as we call them, live for about 4 weeks during the brief Antarctic summer. They build their tiny shells out of calcium carbonate, the main mineral that makes up limestone. By measuring the ratios of two types of oxygen in the carbonate we can tell the temperature of the water in which the forams grew. We will make these analyses on forams that were living in Antarctic surface waters hundreds, thousands, and even millions of years ago to see how warm the water was next to the Wilkes Land coast. We already know from our microscope work on board that this part of Antarctica has been very warm at times, maybe 10 to 15 degrees centigrade warmer when we go back 35 million years. The foram work will help tell us exactly how warm the waters may have been during more recent periods when we know the ice sheet became much smaller. The results will help us predict the behavior of Antarctic ice in the future.

What a trip it’s been! I hope you’ve enjoyed these blogs. If you live in the Bay Area, please look for a notice about a talk I’ll likely give on this expedition in 6 months or so, after we’ve had a chance to start the shore-based part of the work. As we pull ever closer to Hobart we are very much aware that we are simply reaching the end of the beginning.

Christina and Joerg at the bow at sunset. Photo courtesy of John Beck, IODP.

Music by Synthhead. Courtesy of Beatpick.com.

Drilling at Site U1361
Position: 64º 24.6’S, 143º 53.2’E
Water Depth: 3470 meters
11 more days!

ABOARD THE JOIDES RESOLUTION, OFF THE COAST OF WILKES LAND, ANTARCTICA– Hi folks! We’ve been busy the past 9 days. We are coming to the end of our work window here in Antarctic. Summer has ended, the nights are much longer, and next Tuesday we must begin our transit back to Hobart, Australia.

We made our last attempt to get into one of our continental shelf drilling sites but were stopped once more by sea ice. All of the ice here is frozen seawater as opposed to glacial ice.

The sea ice is porous and inside the pores are salty brines that support plant and bacterial life. Here we are trying to collect so ice, but it’s a long way down to the water for this little bucket, especially when working from a moving ship.

We finished drilling deep into the seabed at Site U1359, encountering sediments and rocks that span much of the last 13 million years. For several hundred meters we found layers of rock that alternated between green and brown over distances of 2 to 4 meters. The green parts of the cycle showed evidence of intense mixing of the sediments by animals living at the seafloor while the brown parts showed something quite different – very well-developed laminations that could not have survived if the sediments were mixed. There were different materials in the layers too – some contain more shells of diatoms, the main plant in the surface waters of the ocean. We don’t yet know what these cycles of green and brown represent but we think they reflect the continued glacial-interglacial cycling of the Earth’s climate many millions of years ago.

Today we are in a very cold period in the long-term history of the Earth, and have been for most of the past several million years. Because the Earth is already quite cold, when we have glacial-interglacial cycles, we see large ice sheets coming and going at both poles – in Antarctica, Greenland, and over large parts of North America and Scandinavia. This waxing and waning of polar ice is driven by small changes in the shape of the Earth’s orbit around the sun (it changes from an ellipse to more circular and back again over about 120,000 years), the tilt of the Earth’s axis (it wobbles a bit over 40,000 years), and the exact seasonal timing of when the Earth is at its closest approach to the sun. All of these “orbital” changes impact how much sunlight reaches the Earth as well as when and where it warms the Earth seasonally. Sometimes, the Earth is in an orbital configuration that produces warm winters and cool summers – a combination that usually allows ice sheets to form and grow. Some 10’s of thousands of years later, the opposite occurs – warm summers and cool winters – which can cause ice sheets to rapidly melt. In today’s cold world, these small changes have big effects as the Polar Regions are cold enough to allow large ice sheets to form and last through the warmer periods. Antarctica has been covered in a large ice sheet for many millions of years because of this overall cooling. It still waxes and wanes along its margins but it is always present in the continent’s interior. But prior to about 2.5 million years ago, there was no permanent ice sheet in the north polar regions – it was simply too warm. Further back in time, the Antarctic ice sheet was much smaller than it is today but it was still dancing to the rhythms set by the Earth’s orbit.

What we were seeing at our last drill site and what we are looking for at our latest site is evidence of how these glacial-interglacial cycles affected the Southern Ocean and how they in turn may have been different because the planet was a little bit warmer than today. By studying this we can learn more about how small changes in the planet’s temperature can affect things like ice volume, sea ice extent, and the productivity of the ocean. This is directly relevant to understanding our Greenhouse future. Although all the climate variability that occurred millions of years ago was “natural” (in other words, not caused by people), the strength of the signal that caused these past changes (the orbital changes in this case) is not very different from the strength of the signal we expect from the man-induced increase in carbon dioxide levels in the atmosphere.

The poles are a great place to study both natural and man-induced changes in Earth’s climate because of a phenomenon called polar amplification. We know from many hundreds of studies of the past 50 million years of climate change that whenever the Earth warms up, the poles warm up more than the planet’s average. The converse is true for times of cooling. We don’t yet fully understand the reasons why but based on these studies of the past we shouldn’t be surprised that the poles are warming up very quickly today, at a rate greater than what we see in the tropics or the temperate belts. The cores we collect on this trip have the potential to tell us more about when and why polar amplification occurs.

I’ll send one more blog from this trip once we have cleared our last hole and are heading for Hobart. Sixty days is a long time to be as sea and working every day for 14 hours or more. We are all excited to get home.

I had a chance to get off the JOIDES Resolution a couple of days ago when we were running a “man overboard” drill. We recovered the dummy and then I was able to take these shots. It was our warmest, sunniest, calmest day by far. You’d never know we were in Antarctic waters.

We’ve been seeing lots of whales at our continental rise sites. The whales come to Antarctic waters in summer because of the abundance of food.

At dawn one day, we had more than 35 Humpback whales around the ship. From a distance you usually first see their spout, which you can make out here.

More storms and more icebergs. This seems to be the story around here now. Once each week we get a major blow and the seas kick up.

Then when we are near the continental shelf we see more icebergs…..

ABOARD THE JOIDES RESOLUTION, OFF THE COAST OF WILKES LAND, ANTARCTICA– Finally, after 11 days of transit, we are spudding into our first drill site off the coast of Antarctica. It’s 3AM and we have just finished putting nearly 4 km of drill pipe together and hanging it from the derrick in the photo. The pipe is suspended only 5 meters above the seabed. We are getting ready to retrieve the first section of a sediment core ever taken from of this site, Wilkes Land!

The JR derrick. Currently, it’s supporting nearly 4 km of drill pipe.

The whole ship is abuzz with excitement. Everyone is awake to see what we will get. We will drill up to 1400 meters below the seafloor here over the next 18 days. Will we get back to sediments deposited when Antarctica was lush and green? It seems likely at this point, but first we will examine the age and makeup of the sediments right at the seabed. They should reflect the current glacial nature of Antarctica and maybe even tell us about changes in Antarctica in the recent past, the past few thousand years. We use special tools to collect these soft upper sediments – an advanced piston corer that shoots into the mud in 10 meter sections. This very first core will be on deck in only 30 minutes. We’ll send a special 2 minute video clip for the blog to capture this historic moment. Leg 318 begins in earnest today!

The JOIDES Resolution.

The JOIDES Resolution.

One of the most sudden and dramatic climate changes to impact the earth occurred some 30 million years ago: This was the transition from a Greenhouse World, when ice caps were largely absent and the earth was much warmer, to an Icehouse World with extensive polar ice sheets, exposed land along the continental margins, and glaciers that periodically extended into the lower latitudes. Investigating this climate switch, thought to be mediated by changes in atmospheric carbon dioxide concentration, will help scientists better understand what triggers vast environmental changes that fundamentally affect life on earth.

Ground zero in these studies is the area just off the coast of the East Antarctic Ice Sheet, the world’s oldest and largest polar ice field. By drilling into deep ocean sediments along Antarctica, scientists hope to uncover the earth’s climate history from a time when East Antarctica was largely ice-free, and to investigate its transition to the glacier-covered continent we know today. Investigating this history, and the effect of increased carbon dioxide and other greenhouse gases on polar ice sheets, will help fine-tune computer models and lead to a better understanding of the climate changes we’re experiencing in the present day.

An example of a cross-section of a sediment core.

Co-chief scientist Carlotta Escutia led an international team of marine geologists and climate scientists aboard the JOIDES Resolution, one of the most sophisticated ocean-drilling ships in the world. They set off from New Zealand in early 2010 to drill cores and collect sediment samples off the coast of Wilkes Land, a region of East Antarctica south of Australia that’s thought to have been the final area to become ice-covered during the last great climate transition.Marine geochemists Rob Dunbar and Christina Riesselman from Stanford University reported from this history-making expedition.

Planned drilling locations (yellow markers) for the IODP Wilkes Land Expedition.

Penguins sitting on eggs. In the right-most picture the very busy mate has continued to bring rocks to the nest, to place them on top of the snow.

When storms come the penguin will not leave their nests. To do so would mean their eggs would be blown away or freeze very quickly. During the storm they sit quietly with their face to the wind and wait for it to be over.

Adélie Penguins seem to have a strong sense of where their nest site is even if it is covered with snow! For this group, their sites from last year are under 3 feet of snow. Not discouraged, they simply built their nests on top of the snow pile. How this will affect the egg and chick brooding, hatching and rearing as the snow melts, we are going to find out.

This pair returned to find their long time nest site covered with snow. Instead of building on top of the snow they decided to move elsewhere and found a cozy nest site with a couple of large rocks for protection from the Skuas about 12 meters away. This is nest #3 in our Nest Check and you can follow them throughout the breeding season by seeing the daily pictures here.

Because of their body heat some of the birds are sinking into the snow pile as the days go by. This bird, below, built his nest on top of the pile, but as you can see he is slowly sinking into a larger and larger hole. He is on a nest of a few rocks with two eggs under him. When the female came back it was a challenge to do the nest exchange. We will observe and record the success of this nest.

When the sun comes out and the snow melts, there are small streams everywhere. Small depressions (scrapes) where penguins have built nests in the past fill up with water. This makes it harder to build the nest and the penguins need more rocks. A successful nest will be high enough to keep the egg out of any water run off. The egg will not hatch if it is sitting in freezing water.

The penguins on the left have a challenge to build a dry nest above the water. The third picture shows the result of a poorly built nest in the mud. The egg rolled out and moments later it was picked up by the ever watchful Skuas. The nest shown to the right is a well built nest above the mud, these eggs will be kept dry.

Adélie Penguins are sturdy birds, but stronger and more summer storms pose a challenge to their breeding success. Read how these birds are coping with the effects of climate change here.

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!

One afternoon a young adult female polar bear wandered by the ship. She appeared out of the blowing snow and walked past the stern, fairly close to the ship. An hour later she reappeared and approached the ship, walking up the fantail until she was directly below the railing. Scientists and personnel from the ship were pressed at the railing above, and she just seemed to be curious, sniffing the wind and looking back at us, occasionally pawing the broken ice at the ship’s waterline.

This young adult female bear walked past the ship, eventually coming right up to the ship.

The polar bear, standing just below us at the stern of the ship.

The railing of the fantail where folks are standing is about 5 meters, 15 feet, above the ice where the bear was standing, at the aft end of the ship, the fantail. It was a wonderful chance for people to see this bear up close.

The wind finally dropped below 20 knots for a day and we flew for the bear – only to encounter heavy fog that prevented us from finding her. We located another bear that was a lower priority and we successfully captured her, yielding good data. The next day the fog dissipated and we flew for our priority bear again, but she had moved over 30 miles and we could not locate her until we received a satellite transmission at the end of the day. We remained in the area because this bear was one of the two top priority recaptures remaining, and we successfully located her twice, but both times she was traveling in large areas of broken ice which were unsafe for captures. The temperatures remained warm throughout this period, rarely dropping below 25 degrees; the water temperature remained warm as well, and sea ice simply was not forming very fast.

Poor ice near one of our priority bears.

This is a frustrating aspect of field work: success relies heavily on weather, and the bad luck of encountering stretches of poor weather can put an entire field season on hold. The only thing that can be done is planning. We planned a long field season to provide multiple opportunities to recapture each bear, and we planned on capturing secondary target bears as necessary. Thus, even though strong winds and fog really reduced our flight opportunities and poor ice reduced our capture opportunities, we had successful recaptures of target bears and we were able to process new bears as well.

The poor ice conditions we have encountered are remarkable. Air and water temperatures remained very warm throughout October, slowing the formation of new ice as winter begins. The current distribution of sea ice in the Beaufort is much more typical of late summer than early winter – we have not had to break heavy ice at all in the last 10 days. It is inaccurate to state that this warm October has been caused by climate change; climate refers to long-term patterns of average conditions, not day-to-day weather. Even in a world with an enhanced greenhouse gas effect, some autumns will be colder than normal and others will be warmer than normal. However, climate change is changing what is considered “normal.” As the earth’s climate warms, particularly in the Arctic, the type of weather we are experiencing may become common.

Graph from National Snow and Ice Data Center. Extent of sea ice over the entire Arctic is currently low compared to the 1979-2000 average, in fact, it is nearly as low as the same date in 2007, when the extent fell to a record low.

Today we disembarked from the ship, using helicopters to ferry people and luggage back into Barrow. Although the trip ended on a frustrating note, overall, it was a very exciting success. Every piece of data we gathered is unique – almost nothing is known about polar bears during this time of year, particularly bears out here on the pack ice far out at sea. I cannot wait to return to Laramie and receive data from our shore-based capture crew, which recaptured bears on the coast during the last several weeks. Before any in-depth analyses, it will be informative simply to compare data sets from the bears on ice to the bears on the coast, to see if differences are striking.