I’m


on the ship Braveheart. It’s 1 a.m.


here in Antarctica, and the setting sun turns a nearby iceberg rosy pink. Suddenly, one end of the iceberg tilts up like a sinking ship and crashes back down into the sea. It tilts up again, and then its tip seems to explode. Ice rains down into the sea like shattered glass. I can’t believe my eyes. Hours earlier, my


team and I had anchored Braveheart to that iceberg. We dove into the icy water to explore its cracks and crevices. It was the final stop on our two-month expedition to study icebergs. What we discovered was as stunning as the sudden shattering of this iceberg. Scientists knew little about the ecology


of icebergs until this expedition. From the outside, they look like chunks of floating ice. It’s hard to imagine that anything can live in this frozen environment. Up close, it’s a different story. Life teems on,


under, around, and even inside these islands of ice. Many support a vast food web. Tat’s how matter and energy flow from nonliving things through a series of living organisms.


Diving Dangers I’m here to see how an iceberg food web works, but it’s a risky mission. Icebergs can roll without warning. Just as dangerous, the water is -1.4°C. Tat’s cold enough to kill an unprotected person in minutes. To survive in the cold water, we strap on


heating pads and squeeze into heavily insulated dive suits. We seal all the openings so that no water can seep in. Despite these precautions, we can only stay


in the water an hour at a time. By the end of each dive, the cold has turned our toes and fingers blue and numb. Still, I can’t wait to dive in to see how life thrives here.


4 NATIONAL GEOGRAPHIC EXTREME EXPLORER


Journey to the Sea From a distance, icebergs look white with blue streaks. Up close, I see brown specks stuck in the ice. It’s dirt. An iceberg starts as part of a glacier. As the glacier slowly flows across land, it scrapes the ground and picks up dirt. When the glacier reaches the sea, giant chunks of ice break off and become icebergs. We came to study one of the biggest known


icebergs. When it broke off, it was the size of Jamaica. By the time we arrived in Antarctica, it had broken into smaller icebergs. Now, we see them slowly melting in the summer sun. We’re in a race against time, but conditions


are perfect to explore an iceberg food web. As the sun melts the top layers of ice, it releases trapped dirt into the water. Tere, single-cell plants called diatoms absorb the nutrients in this dirt. Tis helps the plants reproduce quickly. Te population of these plants can double in as little as a day. I see proof of this closer to the iceberg. Te


clear water turns murky green. Soon, I can only see about 6 m in front of me. Surrounded by billions of plants, I know I’m on the right trail to discover the secrets of this food web.


FAST FACT


Diatoms like these produce up to half the energy in the ocean food web.


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