Ocean begins to ‘lose memory’

(ORDO NEWS) — The oceans that surround us are changing. As our climate changes, so do the waters of the oceans, and anomalies manifest themselves not only in the temperature of the ocean, but also in its structure, currents, and even color.

As these changes occur, the normally stable environment of the ocean becomes increasingly unpredictable and erratic, and in some ways the phenomenon is akin to the ocean losing its memory, scientists say.

“Ocean memory – the constancy of ocean conditions – is a major source of climate system predictability beyond weather timescales,” the researchers explain in a new paper led by first author and climate researcher Hui Shi of the Farallon Institute in Petaluma, California.

“We show that ocean memory, as measured by year-to-year persistence of sea surface temperature anomalies, is projected to decline steadily over the coming decades over much of the globe.”

During the study, the team studied sea surface temperatures (SSTs) in a shallow upper ocean layer called the upper oceanic mixed layer (UPM).

Despite the relative shallowness of the MLD—it extends to about 50 meters below the ocean surface—this upper layer of water shows significant stability over time in terms of thermal inertia, especially when compared to the fluctuations seen in the atmosphere above it.

However, in the future, this “memory” effect of thermal inertia in the upper ocean is modeled to decrease globally over the remainder of the century, with much larger temperature variations predicted for the coming decades.

“We discovered this phenomenon by examining the similarity of ocean surface temperatures from one year to the next as a simple ocean memory metric,” explains Hui.

According to the researchers, the effect of shallow water in MLD will increase the level of water mixing in the upper ocean layer, effectively thinning the upper layer.

This is expected to reduce the thermal inertia capacity of the ocean, making the top layer of the ocean more susceptible to random temperature anomalies.

What this means for marine life is not yet clear, but the researchers note that “later impacts on populations are likely,” though some species are expected to be better adapted than others.

In addition, declining ocean memory is expected to make it much more difficult for scientists to predict future ocean dynamics, reducing reliable forecast times for all kinds of SST-related forecasts. This will make it difficult to predict monsoons, marine heat waves (SHWs) and periods of extreme weather.

As extreme weather events are predicted to occur more frequently in the future, our need to accurately predict phenomena such as ocean temperature, rainfall and atmospheric anomalies only becomes more important – but if the ocean loses its memory, we risk going the other way, they say. researchers.

“The projected decline in ocean memory is likely to hamper ocean forecasting efforts by reducing the time that SST forecasts, including those for MSM, are adept,” the authors write.

“Future warming-induced shallowing of the MLD could also alter the statistics of temperature extremes… which, combined with reduced time to predict ocean surface conditions based on resilience, will create challenges for ecosystem management and marine hazard preparedness.”

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