Sea surface microlayer has a hidden impact on climate

Peering into the dynamic frontier where the ocean and the atmosphere meet, we uncover a unique and delicate micro-environment known as the sea surface microlayer.

This thin, yet vital, boundary is teeming with complex interactions that govern the delicate balance between the air and sea.

Sea surface microlayer

Crucially, the sea surface microlayer has enormous implications for nutrient exchange, pollutant migration, and the transport of organic matter between the ocean and the atmosphere. It plays a pivotal role in both local ecosystems and global climate regulation.

A dedicated team of researchers from the University of Delaware (UD) and the University of Georgia (UGA) set out to better understand the fine nuances of this oceanic phenomenon and its role in climate regulation and carbon cycles

The research team faced setbacks on two previous cruises due to stormy weather and the COVID-19 pandemic. However, they remained undeterred, embarking on their third attempt aboard UD’s Research Vessel Hugh R. Sharp.

The goal was to unlock the mysteries of the sea surface microlayer in the North Atlantic Ocean.

Significance of the sea surface microlayer

Andrew Wozniak, an associate professor in UD’s School of Marine Science and Policy (SMSP), emphasized the significance of this ocean layer. He said the sea surface microlayer is a unique micro-environment.

“It accumulates organic material of a certain kind and then reaches the air-sea interface and accumulates there, creating interesting physical properties that influence the exchange of materials back and forth,” said Wozniak.

This delicate balance of materials between air and sea could reshape our understanding of gas exchange and the emission of particles into the atmosphere, explained Wozniak.

Surfactants and atmospheric chemistry

A key focus of the team’s research involved surfactants – compounds that reduce the surface tension of seawater.

“We want to understand what surfactants are in the ocean, how they partition to the microlayer, and what affects their concentration and their composition,” said Amanda Frossard, an associate professor in UGA’s Department of Chemistry.

The research is crucial for understanding how surfactants influence air-sea gas exchange and atmospheric chemistry.

Samples from the sea surface microlayer

Studying the sea surface microlayer presents a host of technical challenges, largely due to its incredibly thin structure, measuring only 100 micrometers -approximately the thickness of a piece of copy paper.

To collect enough samples, the research team repurposed a Rosette sampler, which is traditionally used for deep water sampling.

“We extend the sampler off the back of the boat, dip it in, lift it up and bring it back on board, and then scrape the glass,” explained Wozniak.

This technique allowed the researchers to collect the surfactant molecules clinging to the glass plate as it emerged from the water.

The significance of these surfactants, said Wozniak, lies in their ability to reduce surface tension, which directly impacts turbulence at the air-water interface. “That turbulence is a key factor in how gases can go back and forth.”

Although wind speed has traditionally been the key factor in quantifying gas exchange, Wozniak and his team believe that surfactants play a significant role in influencing these models, which currently have large margins of error.

Future of sea and oceanic research

Once the samples were collected, the team conducted detailed analyses both onboard and back at their respective universities.

Students, including doctoral candidates Felix Agblemanyo and Tia Ouyang from UD, as well as undergraduates Audrey Tong and Ava Grove, contributed to the research, gaining hands-on experience in cutting-edge climate science.

“This was our solution to study the sea-surface microlayer, and it really is a great example of collaboration between the ship crew and the scientists to solve a real challenge,” said Wozniak.

With this foundational research, the team hopes to refine climate models and further our understanding of air-sea interactions, paving the way for more accurate predictions of carbon cycles and climate regulation.

As we continue to strive for a deeper understanding of our oceans and the complex processes at play, this oceanographic research stands as a powerful example of the perseverance and collaborative efforts required in the face of such intricate environmental challenges.

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