FORCLE GLACIER, Switzerland — At around 8,000 feet above sea level, Switzerland’s Forcle Glacier has for thousands of years been deeply ensconced in a frigid mountain valley overlooked by some of Europe’s highest peaks.

To early human hunters who climbed these heights, it must have seemed as if its snow-covered body of ice would forever keep the valley locked in its frozen grip. Whatever was lost on these rocks — iron spears, leather shoes or rudimentary straps — was swallowed by the ice, never to reappear.

But when the Swiss archaeologist Romain Andenmatten arrived here on a recent September day, the ground was so muddy and moist that his shoes sank deep into it. On the ground in front of him lay a leather strap, rimmed with gleaming ice crystals, its holes filled with fine gravel.

The last time a human held it may have been over 1,000 years ago.

As climate change melts glaciers at unprecedented speeds, such ancient artifacts are emerging from the shrinking layers of ice around the world. For archaeologists, this is both a once-in-a-lifetime opportunity and a daunting task as the planet’s rapid warming is exposing objects faster than they can be saved.

When the artifacts emerge from the ice after decades or centuries, many are so well preserved that they seem to have been frozen just hours earlier. European researchers recently grew plants from 100-year-old seeds that had been discovered “frozen in time” in a World War I-era bunker on the Swiss-Italian border. Some of the most scientifically valuable finds are organic, such as wood and leather, which would normally decompose without the ice.