Earth’s ocean floor has a surprisingly powerful effect on climate

Strip away nearly all the land on Earth, and you might expect the climate system to collapse into something simple. New research suggests otherwise.

Even with the land removed, the shape of the ocean floor alone is enough to sustain many of the key features of Earth’s climate.

Testing what the seafloor can do

Peixi Wang, a postdoctoral researcher at Sun Yat-sen University, is the study’s lead author.

“We aimed to better understand the role of ocean bathymetry [the form and depth of the ocean floor, as opposed to land-sea distribution or continental terrain] in shaping the large-scale ocean circulation and global climate,” Wang said.

“Specifically, by retaining realistic ocean bathymetry while removing continents, we investigated to what extent bathymetry alone can sustain the large-scale circulation and asymmetric climate characteristics of the two hemispheres.”

Global climate shapes nearly everything about life on Earth. It determines where people settle, what plants and animals thrive, and how people grow food and build economies. 

Scientists already know topography plays a major role here. It shapes atmospheric circulation, energy transport, and ocean dynamics. 

What’s been less clear is how much of that influence comes specifically from bathymetry.  

Building an ocean world without land

Most of what scientists know about topography’s climate role comes from idealized modeling.

These include atmospheric general circulation models, versions of those models coupled with simplified ocean layers, and fully coupled general circulation models. 

One particularly stripped-down approach is the aquaplanet simulation. This is an idealized version of Earth with land, mountains, and sea ice all removed.

For this study, researchers ran two experiments using the fully coupled Community Earth System Model. 

The first was a control run using present-day Earth’s actual geography, which they called REAL. 

The second replaced all land with a shallow, 10-meter-deep ocean layer while preserving the real ocean’s actual seafloor shape underneath. They called this aquaplanet experiment BATHY. 

A familiar but stronger circulation pattern

The results were striking. Compared with the real-Earth simulation, BATHY retained a broadly similar pattern of large-scale ocean circulation, but the circulation was stronger overall and reorganized in important ways.

As ocean currents shifted, wind systems moved heat around the globe and while Antarctica warmed, the Arctic cooled. 

The seafloor’s shape alone seems to carry much of what’s needed to reproduce these patterns.

“Our results show that ocean bathymetry plays an important role in shaping the global climate system through its regulation of large-scale ocean circulation and heat transport,” Wang said.

Even without continents, realistic seafloor topography sustained the Atlantic Meridional Overturning Circulation (AMOC), although its structure changed.

The circulation weakened above about 1,000 meters but strengthened below that depth, producing a deeper AMOC overall. A Pacific Meridional Overturning Circulation also emerged.

“Notably, hemispheric climate asymmetry persists in the Bathyplanet configuration because of the existence of AMOC, although it is substantially reduced compared with the real-world configuration, highlighting the combined roles of ocean bathymetry and continental geometry in shaping Earth’s climate,” Wang explained.

Broader implications and future research

The shape of the ocean floor isn’t merely a passive boundary sitting beneath the water. It actively regulates coupled ocean-atmosphere dynamics through its control over large-scale circulation. 

It also appears capable of sustaining some of the climate differences between the Northern and Southern Hemispheres even in the near absence of land, although those differences were substantially weaker than on real-world Earth.

These findings carry broader implications beyond just understanding the modern Earth. They could help explain ocean circulation-climate feedbacks more generally. 

They may even offer insight into ancient climates on Earth and climate conditions on other planetary bodies. That includes ocean worlds elsewhere in the solar system, where continents may never have existed at all.

Looking forward, the researchers want to dig deeper into the specific mechanics at play. 

Their next goal is to more precisely quantify how individual features of ocean bathymetry and continental shape each regulate ocean circulation and climate on their own, rather than treating topography as one single combined factor.

“Ultimately, we hope to better understand how ocean bathymetry interacts with other components of the Earth system to shape the global climate,” Wang concluded.

The study is published in the journal Ocean-Land-Atmosphere Research.

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