By its very nature, an engine transforms energy into motion, often employing solid metal components propelled by significant heat. However, engines are not limited to metal constructions. The sun illuminates our Earth. As the elements absorb their radiance, temperatures rise. The heated land and water increase the air temperature above, causing it to ascend and permitting cooler air to glide underneath. Winds journey across the ocean, exerting force on the water, and in return, energy is transferred back to the water in the form of waves.
This represents one of the numerous pathways energy meanders across the terrestrial playground. The ocean is deeply interconnected with the atmosphere and the land, functioning as a cohesive system with the ocean acting as the central power source. It transforms sunlight into subaquatic currents, morphing light and warmth into motion while distributing vital resources: nutrients, oxygen, and trace elements. It molds our coastlines and modulates temperature.
Yet, this engine is far from ordinary; it is the quintessential one. Nevertheless, we refer to this planet as Earth rather than Water.
The Essence of the Oceans
The veil of saltwater enveloping our planet, extending 4 kilometers in depth and 12,740 kilometers in diameter, possesses a fascinating internal composition characterized by temperature and salinity gradients, creating horizontal strata that evolve globally. Currents converge, water ascends and descends, and massive seabed mountain ranges alter the flow.
Deep ocean basins comprise three or four distinct strata, or water bodies with unique traits and histories, generally maintaining their separation.
The thermocline represents the most prominent internal demarcation, signified by a swift temperature shift with depth, primarily denoting the transition from the warm, sunlit surface water to the cooler, shadowy depths below. This generous upper segment connects solar energy and the oceanic engine driven by that warmth.
Ocean temperature has long puzzled mariners. Unlike his peers, Friedrich Wilhelm Heinrich Alexander von Humboldt, a German naturalist born in 1769, perceived nature as a complex network of interrelations rather than fixed categories. Embarking on a 5-year, 8000-km scientific expedition through Latin America in 1799, he sought to gather data to construct a cohesive theory of nature. In 1802, during a Pacific Ocean journey, he encountered an unusual ocean current off Peru. This current contradicted expectations, with temperatures plummeting to 16°C rather than the forecasted 28°C, establishing clear boundaries between warm and cold waters.
It is neither the strongest nor the most significant ocean current nor serves as one of the primary rhythms orchestrating our planet’s life, like the renowned Gulf Stream.
So, what makes this narrow band of cold water along the west coast of South America, ranging from 50 to 200 kilometers in width, so compelling? Its ecological, biological, and economic significance is crucial for South America and the globe. The Humboldt Current is a distinctive phenomenon rooted in paradoxes and anomalies. Its genesis, mechanics, impacts, and even its denomination distinguish it. It is a potent stream of cold water from Antarctica that traverses 5,000 kilometers along the Pacific coast, nourishing the marine food web and underpinning the world’s most prolific industrial fishery since the mid-20th century, extending from Chile to Peru. Humans have long appreciated the exceptional natural assets of the region. From their initial arrival on the continent approximately 14,000 years ago, through the guano collectors of the 19th century, to the Incas who established settlements in the mountains 200 kilometers from the shore, humans have been profoundly shaped by this Current.
A contemporary sea surface temperature chart unveils a strip of cool water ascending the western flank of South America, influencing geopolitics, the Atacama Desert, fishermen — and even swine.
A Unique Taste for a Specialized Market
The vast underwater realm of the Humboldt Current hosts many species, including colossal squids, more than 50 varieties of sharks, sea lions, whales, and additional cetaceans that roam the world.
The leading figure in this brisk Current is the Peruvian anchoveta. Schools of anchoveta inhabit the chilly waters alongside other fish, sea lions, and seabirds, creating a mobile banquet, an unusual occurrence in the open ocean. Investigating the biological sequence uncovers phytoplankton as the foundational link in the food web. These microscopic organisms are not merely sustenance. They are the ocean’s most vital residents, actively transforming solar energy into a form the rest of the food web utilizes. In doing so, they contribute at least 50 percent of all oxygen to our atmosphere and sequester ten gigatons of CO2, approximately 40% of all CO2 emissions, into the deep ocean annually. To provide context, this is akin to the CO2 absorption of 1.70 trillion trees — the equivalent of four Amazon rainforests — every year. All seems well so far.
Once solar energy is captured, the food web thrives. However, it prompts the question: why do these phytoplankton, Earth’s smallest power stations, flourish in the cool Current rather than adjacent warmer waters? This introduces us to a significant effect of the stratified ocean.
Due to Earth’s rotation, a force is applied towards the depths of these exceptionally calm waters, causing them to expand and rise towards the surface. This phenomenon leads to the cooling of the surface water layer, a fundamental factor for the coastal ecosystem, flora, and fauna. Consequently, the seas of Peru and Chile are, on average, ten °C cooler than those of adjacent nations and the Pacific region.
Are you curious why Peruvian anchovies aren’t typical at your local seafood market?
Sea lions favor these small, oily fish, but humans describe their flavor as “distinctive” and “robust,” discouraging widespread culinary use.
In the 1950s, anchovies were primarily ignored by humans. Confronted with plentiful marine resources and wartime shortages, the surplus was fed to pigs. Following World War II, nations like Great Britain promoted food self-reliance, forming “pig clubs” where communities collectively reared pigs, efficiently utilizing household scraps. Yet, conventional scraps could not satisfy the demands for scaling pig production in industrial farms.
In California, sardine fishermen faced a downturn in their industry. The once bustling canneries were now deserted as the sardine population plummeted due to overfishing. Despite warnings from fisheries biologists, about 500,000 tons of sardines were caught each season from 1934 to 1946. By 1947, the industry collapsed. Nonetheless, Californian entrepreneurs, armed with knowledge and capital, ventured to Peru to exploit the anchoveta fishery.
Shifting the focus from canning anchovies for direct human consumption to fishmeal production changed the game. Fishmeal, a dense powder made from fish, especially anchovies, boasts an impressive 50 to 70 percent protein content. Farmers quickly recognized its value, incorporating fishmeal into livestock feed. From 1950 to 1973, global fish catches tripled, yet human consumption remained the same. Fishmeal emerged as a pivotal component of modern industrial agriculture.
Britain, alongside other countries, eagerly imported fishmeal, with half of its consumption allocated as swine feed by 1960. Industrial livestock practices, augmented by antibiotics, facilitated swifter and more cost-effective pig farming. By 1960, Peru had ascended as the leading fishmeal producer globally, accounting for 40 percent of the worldwide fish catch by 1964.
When overexploitation and environmental shifts precipitated a downturn in Peru’s fish yields in 1972, disrupting fishmeal supplies, the cost of British pork escalated almost instantly. The anchovy’s passage from the sea to swine had a tangible influence on culinary offerings.
An Additional Environmental Hazard
The Humboldt Current is exceedingly susceptible to the warming of surface waters. El Niño events, recurring every 2–7 years, precipitate a marked reduction in phytoplankton productivity off the Peruvian coast. This significantly impacts the marine ecosystem, modifying the environmental terrain and food web. Research on the dynamics of productivity shifts during El Niño indicates that both the thermocline and nutricline deepen amidst the transit of coastal-trapped waves. Although the source water depth for upwelling remains stable, its nutrient richness plummets significantly. Combined with an augmented, mixed layer depth, this composes the scenario that hampers phytoplankton growth.
The eastern Pacific Ocean’s warming, attributable to El Niño, is projected to escalate in the subsequent months of 2024, potentially elevating the average global surface temperature by 1.5°C above pre-industrial levels for the first time, following 2023 as the warmest year on record. This cyclical climate pattern is expected to exacerbate the Amazon and Australia’s drought conditions. El Niño has also compromised the ocean’s heat absorption capacity, with these repercussions anticipated to persist throughout the year.
The warming climate induced by human activities is poised to precipitate diverse alterations in marine life. Insights from historical warm periods, such as interglacial epochs, shed light on possible consequences. Salvatteci et al., through the analysis of marine sediment records from the Humboldt Current system off Peru’s coast, discovered that previous warm phases predominantly featured small, goby-like fishes, in contrast to the present domination of anchovy-like species within the ecosystem. This transformation impacts the ecosystem and poses challenges to the global fish stock, given that anchovies are extensively harvested for consumption. In contrast, gobies are more challenging to catch and less desirable as food. Over the past two decades, extreme temperature phenomena have been recorded in oceanic basins, adversely affecting marine biodiversity, ecosystem functionality, and services.
Given the vulnerability of cold-water systems to such alterations, everything reliant on them could undergo abrupt and drastic changes at any moment.
The Unseen Protector
The South American upwelling system, propelled by the Humboldt/Peruvian Current, epitomizes the critical importance of these currents in sculpting our global ecosystem. This narrative is not isolated; it represents a fragment of a worldwide challenge that extends beyond the Pacific, weaving through oceans, bridging continents, and shaping climates.
The Benguela Current off Africa’s southwestern coast, the California Current along the United States’ western coast, and the Canary Current near northwest Africa — all play pivotal roles in fostering marine biodiversity and fisheries by bringing nutrient-dense waters to the surface, ultimately gracing our dining tables.
However, the specter of climate change looms large, casting a menacing shadow over these vital marine arteries. While the dramatic portrayal of the Atlantic Meridional Overturning Circulation (AMOC) cessation in “The Day After Tomorrow” might have captured public attention, the natural unfolding drama does so quietly and with ominous implications.
The Antarctic Circumpolar Current (ACC), the planet’s most formidable oceanic flow, is pivotal in the global climate machinery, safeguarding Antarctica by maintaining its chilly and solid state, thus significantly impacting Earth’s overall well-being. Yet, the ACC faces threats from climate change. Escalating temperatures and shifts in salinity, chiefly driven by anthropogenic greenhouse gas emissions and the depletion of the ozone layer, are disrupting the ACC’s operation. The Southern Ocean, the conduit for the ACC, is witnessing a rise in temperature and a dilution of its waters, leading to changes in water mass density and circulation patterns. Intensified winds, a byproduct of climate alteration, further influence the ACC, enhancing heat distribution and modifying the patterns of eddies, affecting the stability of the Antarctic ice sheet and the biodiversity in the nutrient-rich Humboldt Current.
Amid these challenges, a beacon of hope shines through. After almost two decades of dialogue, adopting the new ‘High Seas Treaty’ by the United Nations on June 19, 2023, marks a pivotal moment in the quest to safeguard marine biodiversity in international waters. These expansive realms encompass two-thirds of the world’s oceans beyond any nation’s jurisdiction. This treaty establishes a legal scaffolding for forming vast marine protected areas (MPAs). It mandates that “genetic materials,” encompassing substances from flora and fauna with prospective applications in medicine or nutrition, should be harnessed for the collective benefit of humanity.
This development should serve as a clarion call for urgent action. Yet, conversations about the ocean are often sidelined and overlooked as an integral component of our daily lives. This narrative is not a mere recount of saline waters; it is a critical chapter in the story of our planet, shaping our weather and climate and influencing economic metrics like GDP, all while absorbing about 30 percent of the excess carbon dioxide we emit into the atmosphere, mitigating global warming but at risk to the very ocean that protects us.
However, the relentless quest for convenience and financial gain, coupled with political apathy towards the repercussions, endangers the fragile balance of these global systems. We continue to emit fossil fuel-driven pollutants into the atmosphere, with so-called “climate leaders” investing hundreds of billions of dollars in amplifying extractions beyond our planet’s tolerance; we treat the ocean as a limitless receptacle for our waste, and we carelessly release toxins that endanger the crucial system upon which we rely. It is disconcerting that figures like Al-Jaber and nations like the UAE are at the forefront, evidently stalling progress and championing the interests of the fossil fuel industry.