Photo: Jeremy Bishop//Unsplash
Think back 20 years. If you’ve even been around that long, odds are your memory of any specific event two decades ago is fuzzy. Sure, you may think that moment is seared into your brain — the sights, sounds, and smells of the moment as clear as day. But surfers, of all people, are proof that a human being’s memory is wildly unreliable. It typically takes us getting about three steps from the water’s edge to forget the size and critical nature of that last ride. Suddenly, dodging a barrel, which was really just a single temporary opening, has morphed into being gloriously spat into safety on a 10-foot wave that wanted to eat you alive. Screw the video evidence that proves otherwise, the moment we tell somebody how big and gnarly a wave was, it lives in our mind as such forever.
The ocean itself doesn’t have this problem, according to scientists.
A study led by researchers at the University of Liverpool has determined that the ocean has a “memory” that lasts as much as two decades. No, they’re not saying the ocean has a hive mind and is more reliable than you when sitting down for beers at the end of a long day of surfing, retelling war stories. The ocean’s “memory,” as the study refers, is its ability to respond to single atmospheric events that impact surface temperature and a delayed ocean redistribution of heat. Specifically, changes in our atmosphere are fleeting and more frequent than long-term changes in things like ocean temperature. However, one is bound to impact the other.
“The study addresses a fundamental question of what ocean memory truly is. The new ocean memory framework reveals physical mechanisms responsible for multi-year ocean memory and paves the way for new methods for evaluating climate models,” said Dr. Hemant Khatri, with the School of Environmental Sciences at the University of Liverpool and lead author of the paper.
The researchers quantified this by studying how the North Atlantic Oscillation influences “decadal fluctuations” (longterm changes in the physics of a system over the course of a decade) in sub-polar North Atlantic Ocean temperatures. They found that temperature anomalies persist, “while being redistributed, in the ocean before dissipating” for one to two decades.
“We find that, in contrast to observation-based estimates, state-of-the-art climate models significantly underestimate ocean memory, estimating it at only eight to ten years,” added Professor Ric Williams, also from the University of Liverpool and co-author of the paper. “This significant discrepancy in ocean memory could have substantial implications for the accuracy of decadal climate predictions from these models.”
