Weather in the deep sea is not as predictable as we thought

Ever wondered about the weather conditions down in the deep sea? Like the silent depths, the answer holds more intrigue and revelation than you might first imagine.

Just the latest word in from a compelling new study published in Nature Geoscience. It seems the deep sea currents, much like our terrestrial weather, are not quite as steady and predictable as we thought.

Weather in the deep sea

The seafloor, the ultimate destination for different kinds of particles, stores a wealth of information. From sand and mud to organic carbon food for seafloor organisms, even pollutants, they all end up there.

These accumulations provide us invaluable clues to past climates, natural hazards, and oceanic conditions. It’s like a historical archive but with data that extends far beyond human records.

Dr. Mike Clare, the leading scientist on the project from the National Oceanography Centre (NOC), paints a vivid picture of the ocean deep. 

“It is important to understand the behavior and pathways of currents that operate in the deep sea, in order to determine pathways of natural and human-made particles and make sense of those records preserved in deposits,” said Dr. Clare.

“However, there have been very few direct measurements made of currents that flow across the seafloor in deep waters. Most are made high above the seafloor, over short timescales, and only at individual locations. Until now we have not understood how dynamic seafloor currents can be in the deep sea.”

Sensing the pulse of the ocean

In a trailblazing effort, researchers from the UK, Canada, Germany, and Italy teamed up. Over four years, they analyzed data from the largest array of sensors ever deployed in the deep sea. 

Thirty-four deep-sea moorings armed with high-frequency Acoustic Doppler Current Profilers (think underwater speed cameras for currents) measured the seafloor currents at water depths up to 2.5 km.

The findings challenged longstanding assumptions. Contrary to previous models that suggested a continuous and steady flow of currents, the data collected indicated that the currents were anything but uniform.

The deep ocean currents were characterized by periods of acceleration, moments of slowdown, and even instances where they reversed direction entirely.

This variability was often influenced by local factors, particularly the irregular relief of the seafloor, which created a dynamic interplay that shaped the flow patterns in unexpected ways.

Such insights not only deepen our understanding of oceanic currents but also highlight the intricate relationships between underwater topography and fluid dynamics.

Insights into deep-sea weather

Professor Elda Miramontes from MARUM – Center for Marine Environmental Sciences and the Faculty of Geosciences at the University of Bremen, is excited by the novelty and the potential implications of these measurements. 

“These are the first measurements of deep-sea currents across such a large area, long duration and so close to the seafloor. This makes them extremely valuable as they will help improve our models for reconstructing past changes related to climate change in the ocean,” noted Professor Miramontes.

“The ocean bottom currents offshore Mozambique are far more variable than we expected,” said study lead author Dr. Lewis Bailey. “Just like currents in the upper ocean, their intensity changes between seasons and can even flip backwards and forwards over the course of several hours.”

Study co-author Dr. Ian Kane said that seeing how these currents behave is a bit like observing the weather in Manchester – always changing and often surprising.

“But observing change in the deep sea is really challenging and, until now, we have had a poor understanding of what background conditions are like in the deep-sea,” noted Dr. Kane.

Understanding deep sea dynamics

Amusing to Dr. Clare, this study underlines the importance of sustained deep-sea observations, which provide critical information on understanding the ocean.

“More detailed observations are critical for understanding the important role bottom currents play in transporting sediment, carbon and pollutants across our planet.”

With these breakthrough findings, we have taken a significant stride towards understanding our oceans better. However, the mysteries of the deep are still far from fully unveiled.

As we continue exploring, what other surprises might the deep sea have in store for us? Only time, and our ceaseless curiosity, will tell.

The study is published in the journal Nature Geoscience.

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