A half century ago, the world changed dramatically. With the launch of Sputnik by the Soviet Union followed by the U.S.'s Explorer 1, the Cold War got a bit colder and the space race officially began.
In today's warmer climate, hundreds of satellites operated by dozens of nations roam the skies, allowing us to see our neighborhood courtesy of Google Earth images and listen to Sirius satellite radio stations during the drive to work. Satellites not only help people stay connected 24/7, they provide an unmatched view from above into subtle changes occurring on Earth today.
The deployment of satellites launched into motion new scientific opportunities to study our planet on a complete range of spatial and temporal scales, from local to global, from minutes to decades. Many scientists at Scripps Institution of Oceanography at UC San Diego count themselves among the beneficiaries of satellites' technological advancements, using Earth-orbiting satellites to tackle global environmental problems in a variety of scientific efforts. Whether they are used to predict weather, map the ocean floor, model atmosphere and ocean responses to climate change, assess the mass balance of ice sheets and sea level rise, investigate natural hazards, track change in Earth's gravity and magnetic fields, or monitor surface changes caused by human activities, satellite data are critical in providing detailed pictures of our home planet.
"Almost anything that we as scientists do nowadays that deals with the planet as a whole can only be done using satellite tools. We cannot easily cover the whole planet with just surface observational tools at an affordable cost," said Bernard Minster, a Scripps geophysics professor and leader of a recent National Research Council Committee study that commemorated 50 years of Earth observations from space.
Scripps geophysicist Helen Amanda Fricker, associate professor in the Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics, uses satellite observations to study the effects of climate change on the Antarctic ice sheet and to understand the processes driving these changes. One of the most dramatic consequences of global warming is sea-level rise, and scientists predict that changes of only a few inches in ocean levels can place coastal cities underwater and disrupt entire ecosystems.
Fricker discovered a complex system of active liquid water lakes that exist beneath the Western Antarctic ice sheet. Only in the last three years have scientists had the necessary tools to detect this complex system of water flowing under the frozen continent.
"We never had data that extended this far south before to make these measurements, and so the lake system went undetected," Fricker said.
As early as the 1970s, scientists had reported seeing subglacial floods but not until Fricker's study last year did anyone know how pervasive the subglacial water system is. These floods were signs of a much more complex ecosystem waiting to be discovered. Using NASA's Ice Cloud and Land Elevation satellite (ICESat), Fricker noticed astonishing changes in the elevation of the ice sheet, up to 10 meters (33 feet) in some locations, signaling a massive movement of flowing lakes beneath.
Ice sheets are actually glaciers of densely packed snow about 2 kilometers (1.2 miles) thick that cover much of the Antarctic continent, 13.7 million square kilometers (5.3 million square miles) of land. The Antarctic ice sheet holds the majority of the earth's fresh water and plays a vital role in regulating the earth's temperature.
This discovery wasn't easy. Fricker and her research team analyzed hours of datasets by individual tracks, a process many other glaciologists considered a waste of time.
"It was an incredibly laborious technique that we came up with for analyzing these repeat-tracks. People couldn't believe we were looking at data track by track but if we hadn't done it in that way, we would have missed these lakes entirely," said Fricker.
The data that led to this discovery was collected by the ICESat's Geoscience Laser Altimeter System (GLAS). GLAS, operating in a near-polar orbit that reaches 86 degrees South, sends a laser beam to measure changes in the earth's surface. These pulses provide "snapshots" through time of the subtle change in the elevation of the ice sheets from the active draining of the lakes below.
Glaciologists around the world are using Fricker's technique to uncover hundreds more lakes under the Antarctic ice sheet. And now this subglacial plumbing system has added a new piece to the already complex sea-level rise equation.
ICESat continues to collect data and now Fricker has more questions that she hopes the satellite data will help answer. With many new subglacial floods to study, she and her research team will continue to analyze the Western Antarctic Ice Sheet to better understand the movement of water through this vast lake system.
As of November 2006, one in particular, Lake Conway, had been draining continuously for 15 months. Fricker believes that as these lake waters flow together they accumulate in a drainage system downstream. The team is also applying Fricker's track-by-track method to other areas of the Antarctica continent and Greenland to find more subglacial lake systems. Her research provides a crucial component that will help scientists improve ice sheet models that will forecast changes in sea-level rise over the next century.
"Knowing where these lakes are, how these lakes exchange water, and how much water is involved will be important to the models," said Fricker.
But these lakes are more than just new scientific avenues to measure global sea-level rise. A pristine ecosystem untouched by humans offers new opportunities for the discovery of unique life forms that may live in these lakes. This could lead to discoveries that may help us understand the origins and future of life on our planet, Fricker adds.
Meanwhile, on the Big Island of Hawaii, hot magma is blazing new trails beneath Hawaii Volcanoes National Park. Scripps professor David Sandwell is using the Advanced Land Observing Satellite (ALOS), launched in 2006 by the Japanese Space Agency, to closely monitor this subterranean volcanic activity.
On Father's Day 2007, the eastern portion of the Kilauea volcano on the Big Island woke up after more than 30 years. The east rift of the volcano, part of a complex subterranean plumbing system, is exhibiting new motion that could affect residents living on the volcanically active island.
Sandwell along with Scripps graduate student David Meyer analyzed data collected by the synthetic aperture radar aboard the ALOS spacecraft in an effort to both examine the accuracy of the satellite's instrumentation and analyze subtle changes to the structure of the volcano system.
"Kilauea started rifting so we decided to look at the data, said Sandwell. "It ended up being pretty spectacular."
Kilauea's caldera, the mouth of the crater, deflated about 10 cm (4 inches) as the magma chamber emptied. The rift, which is directly connected to the underlying dike system, opened 2 meters (6.5 feet). Meanwhile underground, the Pu`u `O`o crater stopped delivering magma to the ocean and started erupting toward the northeast. Observing these minute changes, a capability only available in the last decade, is valuable to understanding the opening of new lava flows and possible future eruptions.
"Before 1995 we would not have detected this movement," said Sandwell.
The tiny cracks that appeared on the well-worn road would have gone undetected by volcanologists if satellites hadn't given them a heads-up.
The United States Geological Survey (USGS) monitors this region very closely. Any change in lava flow direction, such as this one to the northeast occurring at Kilauea, could devastate another densely populated area of the island. Continued satellite observations will be vital to protect lives and property as the volcano actively transforms the landscape of this popular island destination.
In the coming months, Sandwell and colleagues will analyze data captured at Scripps's Pi on Flat Observatory located south of Palm Springs to study what has been occurring beneath the San Andreas fault system in California.
"In the next few years we're going to learn a lot from this satellite," said Sandwell. "It provides much better coverage than any other observation system, allowing us to zoom in on the fault to see changes in the earth's crust at the millimeter level."
Scientists are confident that more and better satellite observations in the future will transform our understanding of the earth's system. These observations can help to minimize the effects of nature's fury and help reduce the human footprint on the natural environment.
Scripps researchers are eager for the next generation of satellites to push science into the future and greatly increase their understanding of global environmental change.
Satellite science still has far to travel. Global observations require long-term datasets and frequent measurements to understand changes in environmental conditions. Current satellites only have a lifespan of about five years and operate on varying orbital tracks. Researchers at Scripps argue that it is critically important to improve instruments and better incorporate time scales as various satellite observations are taking place simultaneously around the globe.
"Just because we can do it doesn't mean the job is done," Minster said.
Fricker sits on the ICESat science team, which is in the planning phase of ICESat 2. Glaciology has transformed since the advent of satellites and subglacial hydrology is becoming an integral part of the ICESat 2 design, according to Fricker.
Science has reached a pivotal point in understanding and modeling the earth's climate system. In order to predict what will happen to the climate over the next 100 years scientists need precise satellite observations to feed their models.
As for the future of science and satellite observation, "what we have learned over the past 50 years of Earth observation from space would have amazed our predecessors. Likewise, what will be known 50 years from now would amaze us today. We need to act upon that knowledge now," said Minster.
By Annie Reisewitz