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World Environment Day: Oceans are feeling the heat

Rising ocean temperatures are affecting the health of marine animals and impacting their ability to survive

A Weddell seal in Antarctica. These seals spend much of their time below the Antarctic ice.(Dhritiman Mukherjee)

By Nitin Sreedhar

LAST PUBLISHED 02.06.2023  |  02:00 PM IST

It’s not just land temperatures we need to keep an eye on. Writing for Bloomberg Opinion in May, columnist and science podcaster F.D. Flam said: “The ocean is like a huge closet where we’ve been able to store 90% of the excess heat trapped by greenhouse gases. That closet is now stuffed. The latest readings from more than 4,000 buoys around the world show record-breaking sea-surface temperatures from January to March this year."

Now, the world is on the cusp of an El Niño event (the unusual warming of southern Pacific waters). That could open the closet door and let the heat and energy spill into our atmosphere. “That’s where the heat buried in the ocean comes back to haunt us," Flam writes.


A humpback whale near Reunion Island. Humpbacks travel great distances every year. Their numbers have dwindled due to commercial whaling. (Dhritiman Mukherjee)

Things are only going to get more complicated. Last month, scientists at NOAA Fisheries, a US government authority on the science and management of fish, other marine life and their habitats, explained in a video how climate-driven changes such as higher ocean temperatures are affecting the health of marine animals—and their ability to survive.

Bottlenose dolphins jump out of the water off the coast of Durban, South Africa. (Dhritiman Mukherjee)

An update from the International Union for Conservation of Nature (IUCN) Red List in December 2022 also highlighted that human activity is leaving marine species devastated. “Most of the Earth’s biosphere, 99% of all liveable space on our planet, is under water. Humanity acts as if oceans were inexhaustible... This Red List update brings to light new evidence of the multiple interacting threats to declining life in the sea," said Prof. Jon Paul Rodríguez, chair of the IUCN Species Survival Commission, a science-based global network that provides information to IUCN on biodiversity conservation.

Southern Elephant seals on the Península Valdés, a Patagonian nature reserve on the Argentinian coast. (Dhritiman Mukherjee)

Dhritiman Mukherjee, one of India’s most accomplished nature and wildlife photographers, has spent years documenting marine animals: from humpback whales near Reunion Island to crabeater seals found mainly around the coast of Antarctica. His photographs are a reminder of what we stand to lose.

A crabeater seal dives into the water, with an iceberg behind it, to evade an orca whale in Antarctica. (Dhritiman Mukherjee)

“The oceans are home to many beautiful species and rich biodiversity. But now that home is not in great shape. There are many problems harming marine life: bycatch (due to commercial fishing operations), a lot of the animals get hit by fishing boats. Plastic pollution is also rampant. The impact of plastic pollution is not that much in Antarctica but it is there to see at many other locations," Mukherjee says on the phone from Kolkata. Incidentally, the theme for this year’s World Environment Day, on 5 June, focuses on solutions to plastic pollution.

Crabeater seals rest on broken sea ice in Antarctica. (Dhritiman Mukherjee)

Mukherjee has seen many of the changes up close. He points to his photograph of crabeater seals resting on sea ice in the Antarctic region. “If you see the character of the sea ice, that is an indicator of global warming," he notes. “The sea ice should be flat and stay intact for a longer time, where these animals rest. But because of the rising temperatures, the ice is melting and breaking faster."

Also read: Climate Crisis: World's oceans hit record high heat in 2022


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