The Ocean Is Starting to Lose Its Memory, Scientists Warn

The oceans are changing. The world's waters are shifting as our climate changes, with abnormality evident in the ocean's temperature, structure, currents, and even its color.

The environment of the ocean is becoming more unpredictable and erratic as a result of these changes, and in some ways it is like the ocean losing its memory.

The persistence of ocean conditions is a major source of predictability in the climate system beyond weather time scales, according to a new paper by researchers.

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

The team studied sea surface temperatures in the shallow top layer of the ocean called the upper-ocean mixed layer.

The upper layer of water is a lot more persistent over time than the lower layer, even though it is only 50 meters down from the ocean's surface.

The effect of thermal inertia in the upper ocean is set to decline globally over the rest of the century, with dramatically greater variations in temperature predicted over coming decades, according to modeling.

We discovered this phenomenon by examining the similarity in ocean surface temperature from one year to the next as a simple metric for ocean memory.

The researchers say that the MLD will cause more water-mixing in the upper ocean, which will lead to a reduction in the top layer.

The lower the ocean's capacity for thermal inertia, the more susceptible it is to random temperature anomalies.

Some species are expected to fare better than others in terms of adaptation, but it is not clear what that means for marine wildlife.

The ocean memory decline is expected to make it harder for scientists to forecast upcoming ocean dynamics, which will reduce reliable lead times for all sorts of predictions related to SSTs. This will make it harder for us to project monsoons, marine heatwaves, and periods of extreme weather.

If the ocean loses its memory, we risk going the other way, as the need to accurately forecast the ocean temperature, precipitation levels, and atmospheric anomalies becomes more important.

The projected decline in ocean memory is likely to hinder ocean prediction efforts by reducing the lead times at which SST forecasts are made.

Future warming-induced MLD shoaling may also alter the statistics of temperature extremes, which combined with reduced lead time for persistence-based predictions of ocean surface conditions will pose challenges for marine hazard preparation.

Science Advances contains the findings.