North Atlantic sees record sea surface temperature anomaly

North Atlantic accumulates unprecedented thermal anomaly

One degree warmer in the water. On the surface, that seems to be all there is to it. But meteorologists are alarmed not by the magnitude alone, but by the extent: for the first time on record, the North Atlantic has shown such a vast area of positive sea surface temperature anomalies. AEMET (Spanish Meteorological Agency) physicist and meteorologist Juan Jesús González Alemán summed it up briefly: "the ocean is already sending signals." The dark patch intensifies between southwest Iberia and northwest Africa, stretching down to Senegal in the subtropical belt.

What the North Atlantic data shows

Records were broken in sea surface temperatures last April, exceeding 21 degrees Celsius on average. The new shock comes from the Atlantic, with figures pointing to an anomaly of around 1 °C above normal, according to science communicator Gorka Orive, who describes the episode as "a massive marine heatwave" spanning millions of square kilometers. US mathematician and climate science communicator Eliot Jacobson published a chart comparing 2023 records with the 1982-2023 average for the same calendar dates: the North Atlantic line visibly diverges from the historical series.

Across the entire North Atlantic, the warm temperature record had been dragging on for over a month. The anomaly is not uniform: it is most pronounced in the stretch off the Iberian coast and northwest Africa, rather than the whole basin.

Anticyclonic winter heated the water

The most common explanation is not exotic. Climatologist Jorge Olcina, professor at the University of Alicante, attributes it to "the succession of anticyclonic winter weeks" that have chained together in the region. A powerful high-pressure system remained hugging the west of the peninsula, blocking storms, worsening drought, and accumulating heat over the water surface.

High solar radiation, atmospheric stability, and air that warmed up and transferred that temperature to the ocean. "That succession of anticyclonic winter weeks is surely behind such localized and intense Atlantic warming," concludes the climatologist, avoiding alarmism but hiding no concern: he says the situation is delicate.

Why worry about a positive rather than negative anomaly?

Here lies one of the cracks in the issue. Some ask why a deviation of +0.8 degrees above average triggers alarms while -0.8 doesn't even make headlines. Others debate the weighting of the data, arguing that moving the average temperature of the entire ocean mass by a tenth is not the same as heating a specific strip by a full degree above normal.

Disagreement usually ends in the same place: the existence or not of scientific consensus and the role of media spreading these warnings. Against the majority position of climate research, claims resurface that CO2 concentrations in the atmosphere are at historic lows and that emissions since the industrial era don't even register on the graph. The reference series used by climate science does not support these theses.

El Niño, the piece that could flip the map

Short-term evolution remains open. With an El Niño phenomenon approaching, already forming in the South Pacific, Olcina is cautious: if we enter a strong El Niño year, the situation will likely normalize, as more cold air masses and DANA events (isolated depressions at high altitudes) and cold drops will reach the area, capable of cooling that part of the Atlantic.

The problem is that nobody knows yet if it will turn into a strong El Niño. The outcome, therefore, is not written: the warm water may stay where it is or may start losing temperature within weeks.

From ocean data to electricity bills

Few topics stray before reaching the core. In the final stretch, the conversation leaves the water and lands in the pocket: taxes, subsidies, the alleged revenue-raising aim of climate policies, and the suspicion that the warning serves to justify another levy on income. Direct disqualification and back-and-forth flat-earth rhetoric consume much of the exchange.

Added to this is the home-brewed meteorological argument: if it snowed in Sierra Nevada, what warming are we talking about? The physical answer is simple —that snow is water that evaporated somewhere— and does not contradict the oceanic data, because a single snowfall and a sustained sea temperature anomaly are different things. The opposite thesis also appears: that there is overwhelming consensus on the human origin of warming and that denial is part of the same package as other unscientific theories.

While the water warns

The underlying mechanism is a vicious circle: higher ocean temperatures lead to more atmospheric warming, and vice versa. Having warm oceans means maintaining heat in the Earth system, because that oceanic heat must escape into the air, doing so very slowly. Hence the most uncomfortable warning: even if emissions stopped, the heat already accumulated in the water would maintain warming conditions for decades.

With that horizon, the North Atlantic episode ceases to be a half-degree anecdote and becomes a signal that may repeat every season. How many summers, how many records, and how many orange maps are needed until the next anomaly stops being debated and starts being counted?