The Top Ten Ocean Stories of 2023

Major discoveries, an undersea tragedy and international cooperation were some of the biggest saltwater moments of the year

Sea Turtle
This year was marked by many broken records in the ocean. Joseph Prezioso / AFP via Getty Images

This year many ocean records were broken as unprecedented heat spread across the Caribbean Basin and as Antarctic peak sea ice dwindled to an all-time low. International cooperation regarding the ocean also ramped up, with countries coming together to discuss deep-sea mining and sign the High Seas Treaty. Scientists also made amazing discoveries, including that resilient animals dwell beneath hydrothermal vents and that innovative paints can be made that mimic the color-changing abilities of cephalopods. In case you missed those huge saltwater stories and others, the National Museum of Natural History’s Ocean Portal team rounded up the ten biggest ocean moments of the year and detailed them below.

Ocean temperature reached new highs

Diver and Bleached Coral
A diver swims past bleached coral. Oceans absorb more than 90 percent of the excess heat resulting from global warming. Lillian Suwanrumpha / AFP via Getty Images

According to the National Oceanic and Atmospheric Administration, by late June approximately 40 percent of the global ocean was already experiencing marine heat waves, defined as periods of unusually warm ocean temperatures. The following month, particularly intense temperature spikes occurred in the North Atlantic and parts of the Caribbean. Southern Florida waters breached 100 degrees Fahrenheit in July, well above the area’s 85-degree average. These striking temperatures are partially explained by the cyclical climate phenomenon of warming in the Pacific that happens every few years, called El Niño. But scientists also cite climate change as a cause, as the ocean absorbs more than 90 percent of the excess heat associated with global warming—and 2023 is set to likely be the hottest year on record. These increased ocean temperatures have led to a variety of problems, from coral bleaching to algal blooms, and are yet another reason to act on climate change.

Scientists discovered a new contender for world’s heaviest animal

An artistic rendition of what Perucetus looked like Alberto Gennari

The blue whale has enjoyed the weighty title of the largest animal ever to have lived. But the discovery of a gargantuan fossil, named Perucetus colossus, challenges the blue whale’s claim as the heaviest animal ever, according to a study published in Nature in August. Archaeologists discovered the 40-million-year-old bones of Perucetus in the southern Peruvian desert. The individual, which may have weighed up to 400,000 pounds, likely belonged to an extinct group of whales called basilosaurids, which dominated the ocean up to 45 million years ago. Dense bones helped the animal stay near the ocean floor for feeding. Scientists uncovered 13 vertebrae and a few other bones, but they hope to find more pieces of the animal, which may inform how the whale lived and ate.

The Titan submersible imploded on a trip to the Titanic

Ship Searching Ocean for Titan
A Coast Guard plane searches for the Titan submersible in the Atlantic Ocean. Remnants of the sub were recovered in October. U.S. Coast Guard via Getty Images

This summer, five passengers on the submersible Titan were killed while on a tourist voyage to see the wreck of the Titanic. The vessel, operated by OceanGate, lost communication 1 hour and 45 minutes into a scheduled eight-hour dive on June 18. The vessel failed to resurface at the scheduled time later that day. After an international search lasting four days, the U.S. Coast Guard said debris had been found that indicated a catastrophic implosion of the submersible. Before the sub went down, experts had warned that the experimental approach to designing the vehicle could lead to catastrophic problems. Stockton Rush, the CEO of OceanGate Expeditions, who went ahead with dives anyway, was one of those who died in the implosion.

Scientists discovered a thriving ecosystem beneath the ocean floor

A cluster of tubeworms on the East Pacific Rise, the same region where tubeworm larvae were discovered under the earth’s crust ROV SuBastian / Schmidt Ocean Institute

Along the East Pacific Rise, a tectonic plate boundary off the west coast of South America, lives a vibrant deep-sea community of tubeworms and other animals reliant upon the heat and nutrients emitting from a hydrothermal vent. This year, scientists discovered a community of animals also living below the seafloor beneath the hydrothermal vent. Hydrothermal vents occur when cool water meets magma, resulting in streams of gas up to 700 degrees Fahrenheit. Animals like the tubeworm (Riftia pachyptila) live around these vents, but until recently scientists did not know how they moved from one vent to another. Often, these vents can be miles apart. Using a remotely operated vehicle to turn over chunks of volcanic crust at a depth of 8,200 feet, a team of researchers discovered that the animals could travel through crevices beneath the seafloor. The researchers exposed a network of tunnels containing tubeworms, snails and slithering worms in an area previously thought inhospitable to animal life.

Octopus camouflage inspired a color-changing paint

Octopuses use the pigments in their chromatophores to rapidly change their appearance. Alexis Rosenfeld / Getty Images

Octopuses and other cephalopods are masters of disguise; they can rapidly change their appearance thanks to small organs within their skin called chromatophores. These tiny sacs contain xanthommatin, a natural dye. This year, scientists at Northeastern University made a synthetic version of xanthommatin that can be mixed with titanium dioxide to create a solution that changes color between red and yellow when exposed to light. According to the researchers, this technology could be used for artwork that changes or as an environmentally friendly alternative to regular paint.

Medieval Europeans likely helped drive whales to extinction

North Atlantic Right Whale
A North Atlantic right whale, the same species medieval Europeans may have helped hunt to local extinction David L. Ryan / The Boston Globe via Getty Images

The intense whaling practices of the 19th century often take the blame for imploding whale populations across the globe, but new research indicates medieval whaling may have contributed to the depletion of numerous whale species in European waters. To determine whether humans impacted medieval whale populations, scientists inspected 719 bone specimens found throughout Europe that dated from between 3500 B.C.E. and the 18th century. Many of the specimens were associated with cultures frequently linked to whaling. The researchers found out that the majority of these specimens belonged to the now extinct Atlantic gray whale and the North Atlantic right whale, an endangered species. This finding suggests that medieval European whaling practices influenced the overexploitation and local extinction of these whales.

Deep-sea mining decisions were delayed

Brittle Star
A brittle star swims over a field of polymetallic nodules. Craig Smith and Diva Amon / University of Hawaiʻi at Mānoa

The deep sea contains valuable metals such as nickel, cobalt, manganese and copper in potato-sized rocks called nodules. Mining companies and countries have expressed interest in mining these resources for use in renewable technologies. Meanwhile, nongovernmental organizations, some companies and at least 23 countries have called for a moratorium or precautionary pause on the deep-sea mining industry. Experts fear that mining could negatively impact carbon sinks and ocean life, including still-unidentified species near the ocean floor. This year, the International Seabed Authority agreed to finish deep-sea mining regulations by 2025. But at least one deep-sea mining firm may be allowed to begin mining in 2024, before regulations are in place.

Antarctic sea ice entered a new era of decline

Antarctic Sea Ice
Clumps of sea ice in Antarctica, where ice is melting at alarming rates Kerem Yuce / AFP via Getty Images

According to a study published in Nature, this February a new daily minimum Antarctic sea ice extent was observed. And this September, the peak sea ice coverage in Antarctica reached an all-time low since records were kept beginning in 1979. While sea ice had remained somewhat stable until 2016, things have gotten worse in the last seven years. According to a statement released by the National Snow and Ice Data Center, some are concerned that low levels may be the start of a long-term trend of decline for Antarctic sea ice, due to oceans warming globally and warm water mixing in the Southern Ocean polar layer. Lower levels of sea ice can lead to declines in animal populations and cause land ice, unprotected from a warming ocean, to melt faster—causing sea levels to rise.

Orcas interacted with boats

Killer Whales
Orcas are adopting a new behavior of ramming sailing boats. Sylvain Cordier / Gamma-Rapho via Getty Images

Orcas off the Iberian Peninsula rammed, damaged and sometimes sunk boats this year. The Atlantic Orca Working Group reported a 298 percent increase in interactions between the animals and boats from 2020 to 2023, with more than 500 incidents recorded during that time. Of these incidents, at least four in the past two years have resulted in a sunken ship. One of the most recent incidents was a 45-minute encounter off the coast of Morocco on October 31, where orcas slammed into the boat’s rudder, causing a leak. The damaged yacht could not be rescued, but the crew was fortunately unharmed. Most of the orca interactions seem to be caused by around 15 orcas from a population of less than 50, but observed occurrences farther north indicates that this behavior is spreading to other members of the species. Researchers think this new behavior is a fad, like many others by the highly intelligent and social animals.

Over 70 countries signed the High Seas Treaty

Vessel at Sea
The high seas are parts of the ocean that are not under national jurisdiction. Owen Humphreys - PA Images / Contributor via Getty Images

In a monumental win for ocean protection, the European Union and more than 70 countries, including the United States, signed the High Seas Treaty at this year’s United Nations General Assembly. The treaty, also known as the Biodiversity Beyond National Jurisdiction agreement, aims for protection, conservation and equitable profit from the high seas, or areas of the ocean outside of individual countries’ jurisdiction, which typically start about 200 nautical miles, or 230 miles, from the coast. Under the treaty’s goals, 95 percent of the ocean’s volume would be under common governance, and special marine protected areas would be established to limit overfishing, shipping and deep-sea mining. The treaty had been a work in progress for nearly 20 years. Now, 60 of the signatory nations must ratify the treaty by their own procedures before it can come into effect. Once it does, experts say, there will be huge benefits for restoring planetary health.

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