Operation Antarctica
 

Antarctic morning of December 2004 found Brian Stone peering at his computer screen. Miles away, across McMurdo Sound, two icebreakers were carving a path through the sea ice to the American base where Stone was waiting their arrival. Behind the icebreakers followed a fuel tanker and a cargo ship carrying critical supplies for McMurdo Station, the U.S. Antarctic research hub. Between the approaching ships and McMurdo, four massive icebergs lurked dangerously close to the shipping channel.

As Research Support Manager for the National Science Foundation’s Office of Polar Programs, Stone was charged with the nuts and bolts of running a large research program on a vast, frozen continent. Among his responsibilities, Stone had to figure out how to get supplies to 700 researchers and more than 1,000 support personnel at three Antarctic research stations and numerous remote field camps. Getting the re-supply ships to McMurdo was just the first stage of the effort. From there, Stone would have to arrange for the supplies to be ferried by airplane to the other U.S. stations and field camps.

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(Image in title graphic courtesy National Science Foundation)

  Edge of Iceberg B-15
 

The icebergs creating traffic problems in the Ross Sea that December were the most recent foe to be added to his list of everyday obstacles, including bitter cold, sudden fog, fierce winds, and blinding snow. Furthermore, Stone has to deal with all these problems without the extensive network of ground-based, weather-observation stations that forecasters and planners in less remote locations can take for granted.

In a place where on-the-ground data are scarce, Stone and others operating research projects on our planet’s least-hospitable continent have been getting the upper hand on the extreme environment through satellite observations, including photo-like images, from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) on the agency’s Terra and Aqua satellites.

Later in the season, MODIS might be able to provide valuable information about clouds, wind, and water vapor to the weather forecasters who helped Stone plan flights. But at that moment, it was the ships that most worried Stone. As Stone checked his computer for the twice-daily delivery of MODIS images of the Ross Sea, what he wanted to know was exactly where the icebergs were moving.

 

The massive B-15 iceberg that calved off the Ross Ice Shelf in 2000 eventually broke into several bergs that created navigation problems for ships supplying McMurdo Research Station in Antarctica in 2004. Josh Landis took this picture of the edge of the Rhode-Island-sized B-15A iceberg in 2001. (Photo courtesy Josh Landis, National Science Foundation, AWS/AMRC Photo Gallery)

 

A Battle with Bergs

 

The icebergs moving around McMurdo Sound in the summer of 2004 and 2005 had spent the previous four years anchored fast near Ross Island, but by December 2004, two had swung free and were moving through the very waters Stone was trying to get supplies through. He might be able to plot a course around the icebergs, but what would he do if one of the icebergs moved into the shipping channel or trapped the supply ships? It was as if Stone were a highway planner trying to devise a detour around a pothole larger than the state of Rhode Island that moved unpredictably across the road. And the “pothole” had three smaller companions whose sizes were still best measured in kilometers.

The largest of the quartet was the B-15A iceberg, which measured 122 kilometers long by 28 kilometers wide in late 2004. The second iceberg, C-16, was only a quarter of the size of B-15, but was still 48 kilometers long by 18.5 kilometers wide. The other two bergs, B-15J and B15-K, had broken from B-15A and measured 56 by 41 kilometers and 59 by 9 kilometers, respectively.

In November 2004, B-15A had started to drift away from Ross Island and blockaded McMurdo Sound, freeing the way for B-15J to move. Its timing couldn’t have been worse. Supply ships were scheduled to arrive in Antarctica at the end of December and early January, and the fast-moving B-15A iceberg was blocking the northern section of the traditional shipping route. Meanwhile, the still stationary B-15K iceberg blocked the southern portion of the route.

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Satellite image of B-15

Icebergs blocked McMurdo in late 2004 and early 2005. MODIS acquired this image of B-15 in February 2005.

  Icebreakers

“We were really, really worried at how we were going to supply McMurdo Sound,” confides Stone, deep concern evident in his voice even months after the end of the season. To get the ships safely to McMurdo Station, Stone needed to know where the icebergs were going on a regular basis. When the bergs started to move, he turned to MODIS, a sensor on NASA’s Terra and Aqua satellites that collects daily imagery of the entire Earth.

 

U.S. Coast Guard icebreaker Polar Star (left) and U.S. Navy tanker USNS Paul Buck broke ice near McMurdo in February 2005. (Photo courtesy National Science Foundation)

 

MODIS Rapid Response

 

“I had gotten a MODIS image from a researcher,” Stone recalls. He had been impressed with the quality and detail of the photo-like images. Compared to some kinds of satellite images, says Stone, “True color seems more like you’re looking at a photo. You can identify features easily.” While being able to identify features easily made the images easy to use, timeliness was also essential. If he were going to use satellite imagery to direct the supply ships to McMurdo, Stone needed the images immediately after they were acquired, not days later.

The MODIS Rapid Response Team at NASA Goddard Space Flight Center was ideally set up to give Stone the images he needed. Developed in 2000 to monitor wildfires across the world, the MODIS Rapid Response System posts all MODIS images of land on the Internet within hours of when MODIS acquires them. The images are free and accessible to anyone who has an Internet connection.

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  Shipping channel
 

Stone’s request for imagery came at a fortuitous time. The Rapid Response Team had recently started to produce daily images of selected regions that were compatible with Geographic Information System (GIS) mapping programs so that other information—like a shipping route—could be placed on top of the images. By contrast, the near-real-time global imagery the team had been distributing up until that point was not processed to the level that it could be used as the basis for a map.

“When the request came in, we thought this was a typical application we should help with,” says Jacques Descloitres, program manager of the MODIS Rapid Response System. The team started generating daily images of the Ross Sea.

Stone was delighted. “We had never had a full view of McMurdo Sound before,” he says. “Then someone set up this site that was capturing our part of the world that everyone could look at for free, and it was updated on a daily basis.” The site quickly became the first thing Stone looked at every morning.

 

MODIS acquires images of Antarctica on a daily basis. This MODIS image shows the McMurdo shipping channel along with other features of the icy continent. The turning basin is a wide arc cut into the surrounding ice so that icebreakers and other ships can turn around. (Photos courtesy MODIS Rapid Response)

 

Mapping with MODIS

 

Using the detailed, near-real-time imagery that appeared on his computer screen each day, Stone detoured the ships through the gap between what seemed to be the safer, predictably lodged icebergs B-15K and C-16, neither of which had moved in the past 3 years.

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  C-16 bathymetry
 

“To everyone’s surprise, C-16 began to move slightly the afternoon of January 8, and by January 11 was moving in earnest, making the prospect of a blocked shipping channel a real concern,” says Jessica Walker, GIS analyst with Raytheon Polar Services, to whom the task of tracking the icebergs in the MODIS imagery fell. “C-16 sometimes barreled forward,” she says. “After 3 years of not moving, it jumped 7.5 kilometers north about the same time as the ships were moving in fuel and supplies.”

Walker had been making regular animations of B-15A, which was hurtling towards the Drygalski Ice Tongue, the floating extension of the David Glacier over the Ross Sea, on a direct collision course. A direct collision between the largest moving object on the planet and a roughly 75-kilometer-long spit of ice could make for an exciting show, a demolition derby on a gargantuan scale. “Everyone wanted to see the collision and wanted to document it,” says Walker. “I couldn’t even go to the coffee house without someone asking me about the iceberg. It was neat being able to provide critical information of such a significant event.”

 

Bathymetry data outline the contours of the sea floor around the C-16 and B-15K icebergs. Since the icebergs were most likely to move along the deep channels, the bathymetry helped the U.S. Antarctic Program predict where the icebergs might drift and where it would be safest to cut the shipping channel through the ice. Image by Jesse Allen, Earth Observatory, based on data from Jeff Schmaltz (MODIS Rapid Response Team), Jessica Walker (Raytheon Polar Services) and Fred Davey (Institute of Geophysical & Nuclear Sciences Ltd.)

  B-15A edge
 

A countdown to collision ensued, but B-15A defied predictions and ground to a halt mere kilometers from the ice tongue. Bathymetry information overlaid on the MODIS images showed exactly why the iceberg had stopped; it was grounded. The bathymetry images also explained why the iceberg later rotated and drifted into deeper waters in the Ross Sea, sideswiping the tip of the ice tongue as it went. The massive berg was following the deeper channels of the sea. “When you look at the image, you realize it was the only way the iceberg could move,” says Walker.

Despite the anticlimax of B-15A’s movements, Walker’s practice at making animations and bathymetry images now stood her in good stead as she turned to track C-16, a much larger operational concern. The bathymetry maps showed a shallow shoal to the west of the shifting iceberg, which she hoped would keep the berg out of the shipping channel.

The Coast Guard, whose icebreakers were keeping the channel clear, began to watch the MODIS imagery closely. “The captains were concerned that C-16 would rotate in and close off the channel. They worried that it would be hard to get their ships out,” says Stone. The captain of a Russian icebreaker hesitated to enter the channel at all. Stone brought the MODIS images to the ship to reassure the caption that the ship’s crew could watch the icebergs’ movements daily. “I don’t know if he used the images, but he brought his ship through the channel to McMurdo,” says Stone.

 

The B-15 iceberg was already a navigational concern when Josh Landis photographed it on a November 2000 excursion. GIS specialist Jessica Walker combined satellite images with underwater topographic data to predict the movements of one of the giant iceberg’s largest pieces, B-15A, as it moved toward a collision with an ice tongue in the Ross Sea. The analysis was good practice for predicting the movements of other icebergs in the shipping route to McMurdo Station. (Photo courtesy Josh Landis, National Science Foundation, AWS/AMRC Photo Gallery)

 

Combating the Weather: MODIS Predicts Flight Hazards

 

With McMurdo supplied, the next hurdle Stone had to face was sending airplanes to the other bases and camps to distribute the supplies. This time, the continent’s nearly constant hostile winds, blowing snow, and heavy fog stood in his way. Forecasters in Antarctica provide flight forecasts to keep airplanes as safe as possible, but with few weather-monitoring stations to give them accurate information, their ability to predict severe weather is limited.

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Even as Stone was watching icebergs in the Ross Sea, Matthew Lazzara and Jeff Key, researchers from the University of Wisconsin-Madison, and Andy Archer, a remote-sensing analyst for Raytheon Polar Services, were installing a station at McMurdo to download MODIS data directly from Aqua and Terra as they pass over Antarctica.

While the photo-like MODIS Rapid Response images Stone had used to track icebergs were perfect for showing people the current conditions in Antarctica and for making maps, they became available two to three hours after being acquired, when the satellites passed over North America. But in addition to sending down large chunks of stored data at specific stations across the globe, MODIS also continuously broadcasts the data it is collecting via X-band frequency radio. Weather forecasters need data quickly, and data from a direct broadcast receiving station such as the one Lazzara, Key, and Archer installed in Antarctica arrive instantly. These “instant” data help to monitor current weather conditions, augment weather maps, and refine predictions.

  C-141 airplane

A C-141 airplane makes a delivery to McMurdo Station. Predicting when the weather is safe for flying in Antarctica is especially challenging because ground-based weather stations are scarce. (Photo courtesy Ted Scambos, National Snow and Ice Data Center)

  Infrared satellite image of Antarctic weather

The station was installed at the end of the season, and started operating in April 2005. As such, it couldn’t help Stone plan flights during the 2004-2005 season—it has yet to be tested operationally—but it could improve forecasts during the 2005-2006 season. “It’s brand new to us,” says Art Cayette, the Meteorology Executive Agent for the U.S. Antarctic Program. He’s anxious to return to the ice to try out the new system. “We’re the perfect place to experiment with remote sensing,” he observes. “We have very little real data, so we can really see the effect each new tool has on forecasting models.”

 

This infrared Antarctic composite is a mosaic of data from several satellites. This image shows Antarctic cloud conditions on September 6, 2005. (Image courtesy AWS/AMRC Antarctic Composite Satellite Images)

 

Clearing up Fog Formation

 

One of the problems he hopes MODIS can solve is predicting fog. Thick fog can materialize very rapidly, explains Cayette, and it poses a serious hazard to planes and boats. One airplane was coming in on approach for a landing, recalls Cayette, when the pilot suddenly lost the runway in a field of white. It took the pilot a few seconds to realize that fog had instantaneously obscured the ground for miles in every direction.

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  Antarctic fog

Such fog is difficult to predict, but MODIS may soon help forecasters see farther into the future. Typically, forecasters can predict fog by observing moisture in the atmosphere, but tracking increased water vapor on or near the surface requires a comprehensive network of sensors, such as the National Weather Service Stations and radar networks in the United States. In other parts of the world, the presence of clouds also indicates where the air is moist enough to produce fog. In Antarctica, however, clouds don’t form as readily in the cold, pristine air, and with fewer ground sensors, pockets of extremely moist air often aren’t detected until they settle to the cold ice surface and form visible fog.

 

Fog and low clouds obscure the view of a mountain near Palmer Station on the Antarctic Peninsula. In Antarctica, fog can materialize suddenly, becoming a serious flight hazard. (Photo courtesy National Oceanic and Atmospheric Administration Photo Library)

  Antarctic fog and clouds in true- and false-color images
 

“No one has really studied fog in Antarctica,” says Lazzara, but he’s hoping that MODIS will help him understand why fog forms so quickly and how its formation can be predicted. MODIS provides a fuller picture of water vapor and fog formation than other satellite instruments because of its multispectral resolution, says Lazzara. When MODIS collects images of the Earth, it “sees” all of the components of visible light as well as thermal, shortwave, and near-infrared energy. In all, MODIS collects 36 different groups of wavelengths of energy, or spectral bands, and this wide range (or multispectral resolution) will let Lazzara distinguish fog from snow or other low clouds and observe atmospheric water vapor.

 

Fog and clouds can be hard to distinguish in the true-color image (left). The false-color image (right) shows clouds in white and fog in blue. High-resolution versions are available for the true- and false-color images. (Image by Jesse Allen, Earth Observatory)

 

Winds and Flight Forecasts

 

A more immediate application of MODIS data is in observing polar winds. Jeff Key has already started to track winds over Antarctica based on cloud movement using MODIS. Better measurements of wind speed extend the accuracy of weather forecasts generated by forecasting models. Before they completed the ground station that lets them receive MODIS direct broadcast data in real time, Key had to wait for the satellite to reach North America to get the data it collected over Antarctica. Now, the station receives the data MODIS collects over Antarctica instantly, and that will let forecasters in Antarctica update their models more quickly. (To learn more about how MODIS improves weather forecasts, see "Polar Wind Data Blow New Life into Forecasts" on the Earth Observatory.)

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  Twin otter
 

“The station will have multiple benefits,” predicts Lazzara. The station is capable of receiving data from multiple sensors, including additional instruments on the Aqua satellite. “Forecasters don’t always get to see the latest and greatest, but in this case, they do.” Among the benefits of the new station, Cayette hopes that MODIS will help him predict more flight hazards like blowing snow and low clouds—something he has had some success with using data from the MODIS Rapid Response Website.

Heading Home

The stations supplied for the long winter, and the direct broadcast station installed and running, Stone and the others returned to the United States. They will spend the summer (North American summer, that is) making plans for the 2005-2006 research season, and those plans already include MODIS.

 

A Twin Otter aircraft perches on the C-16 Iceberg. (Photo courtesy Shelley Knuth, AMRC/SSEC/UW-Madison, AWS/AMRC Photo Gallery)

  McMurdo

Three icebergs linger near McMurdo and the shipping track, and B-15A is about to move out of the Ross Sea. While MODIS will continue to be used to track their positions, Stone is already envisioning other applications.

“In the early part of the season, we do a lot of work on the sea ice. MODIS will let us see what is going on with the ice,” says Stone. He will be looking for the edge of the ice and tracking large cracks to help plan safe locations for field camps. He hadn’t used satellite imagery extensively in the past because he hadn’t been able to access it easily. Now, reflects Stone, he asks for a MODIS image before planning anything.

“MODIS got us addicted to daily imagery,” says Stone. “Expectations are different now. Now it’s easy. I love MODIS.”

As for the weather team, Cayette sums up their MODIS plans. “We’re chomping at the bit to get down there and find out what we can do.”

  • References
  • Davey F.J. 2004. Ross Sea Bathymetry, 1:2,000,000, version 1.0. Institute of Geological & Nuclear Sciences geophysical map 16. Institute of Geological & Nuclear Sciences Limited, Lower Hutt, New Zealand.
 

Quickbird captured this image of McMurdo Station, the largest human community in the Antarctic. (Image copyright Digital Globe)