"Follow me," Kirk Martinez says as he leaps from boulder to boulder, his shoulder-length brown hair trailing behind him. I try to keep pace, striding along the trail, a bitter wind against my face. We stop at the base of a wall of rock that rises more than a thousand meters. From behind that mountain, what looks like a huge river of snow snakes its way to where we stand. But as we move closer, one thing becomes clear: this enormous swath of bluish white is not snow—it's ice.

It's a bright August morning in the tiny bucolic town of Olden, in southwestern Norway, and I find myself about to clamber up the largest mass of frozen water I've ever seen. It's called the Briksdalsbreen. Breen, I am told, is Norwegian for glacier, and Briksdalen is the picturesque valley where it resides. Although it holds more than a billion tons of rock-hard ice—enough to fill up a thousand Empire State buildings—Briksdalsbreen is just a small arm of a much vaster glacier named the Jostedalsbreen, which, boasting an area of almost 500 square kilometers, is the largest ice field in continental Europe.

"Time to put on the gear," Martinez says, grabbing a helmet and an ice axe. He climbs onto the ice first, and again I try to follow him. "Keep your feet apart and walk with short, firm steps—and don't run," he cautions me. As we trudge onward, our crampons—spiky metal contraptions strapped to the bottoms of our boots—bite into the ice, making a satisfying sound: crunch, crunch, crunch....

Martinez, a professor of computer science at the University of Southampton, in England, is here, along with a squad of engineers and glaciologists, to field-test a wireless monitoring network specially designed to study glaciers. The system's key component is a capsule that the researchers have stuffed with environmental sensors. The plan is to embed dozens of these probes deep within this huge tongue of ice, where they will record temperature, pressure, and other variables for several months.

While Martinez is in charge of the group's electronics work, Jane K. Hart, a geography professor at Southampton, leads the glaciological investigations. This husband-and-wife team has been working on the project, called Glacsweb, for almost five years. They aim to tackle one of the most challenging problems faced by glaciologists today: understanding how Earth's ice masses will respond to the continued warming of the globe. Glaciers in the Alps, the Andes, Alaska, and central Asia have been rapidly shrinking, contributing to sea-level rise and often causing floods. But will others follow the same course? Will the glacial shrinkage accelerate? The Glacsweb system could shed light on these and other issues by allowing scientists to "see" with unprecedented detail what goes on deep inside glaciers.

Wireless sensor networks are spurring a revolution in environmental monitoring, with researchers using them to keep tabs on crops, rivers, volcanoes, and even birds [see "The Secret Life of Birds," April 2004]. The Southampton team is one of the few applying such networks to the study of glaciers. Their wireless probes could prove a good replacement for some of the conventional instruments used by glaciologists, like gauges that are also embedded in the ice but with wires running to the glacier's surface. The problem with these wired devices is that their cables are often broken as the ice around them deforms. The British researchers chose the Briksdalsbreen because it is relatively accessible and is particularly sensitive to climate fluctuations. During a previous research trip here, they deployed nine probes. Now they are back with more.

With about a ton of equipment, the British researchers figured it would be too expensive to fly in. So they packed their cargo into two large vans and drove from Southampton, on the English Channel, to Newcastle, in the northernmost part of the country, where they boarded a ferry and headed across the North Sea. A day later, they disembarked in Bergen, Norway's second largest city. From there, it was a 6-hour drive to the Melkevoll Bretun, a campsite near the Briksdalsbreen, where the group rented three cabins to serve as their base of operations.

When I arrive for my weeklong stay, the researchers have already been here for nine days. The cabin I'm bunking in has been transformed into an electronics laboratory. The dining table, pushed against a wall, serves as a workbench, equipped with an oscilloscope, spectrum analyzer, soldering iron, voltmeter, and computer. The windowsills are cluttered with small boxes of spare electronic components. And on the floor, dozens of batteries and transformers and a maze of cables are piled up near a power outlet.

That night, after dinner, I find Ahmed Elsaify, an Egyptian who has just joined the Glacsweb group as a postdoctoral student, hunching over the improvised lab bench. He holds a chunk of circuitry the size of a kiwifruit up before his eyes, examining it meticulously. It is a probe's electronic innards, he tells me, and it includes six lithium batteries, a bunch of sensors, a 64-kilobyte memory for data storage, a radio transceiver, and an antenna; it also has a 16-bit microcontroller—the brains of the device—and a real-time clock chip, which wakes up the normally dormant electronics at specific times [see photos, "Preparing the Probes"].