The global climate picture has gained yet another wild card: “mesoscale turbulence” in ocean waters.
Mesoscale turbulence appears to affect the movement of water across sections of ocean 30 to 120 miles in reach, scientists Julius Busecke and Ryan Abernathy reported in Science Advances earlier this month.
These movements, they wrote, affect heat, salt, nutrients, and oxygen and carbon, the two key components of the hot gas of the times: carbon dioxide (CO2).
“This transfer of CO2 out of the ocean to the atmosphere is referred to as a positive ‘flux’ while a negative flux means that the ocean is absorbing CO2,” according to the National Oceanic and Atmospheric Administration. “The ocean has a complicated pattern of both positive and negative fluxes. Prior to the Industrial Revolution and the burning of fossil fuels, the net global ocean flux was slightly positive to offset the absorption of CO2 from the land plants. Today, humans have reversed that trend so the oceans absorb more CO2 than they release although the complicated pattern of positive and negative fluxes still exists.”
Little is now known about that complicated pattern.
Given this, Busecke and Abernathy concluded in their peer-reviewed study that it is now “critical to investigate whether and how mesoscale diffusivities change over time, a possibly missing element in future climate projections.”
A postdoctoral research associate at Princeton University, Busecke said there is at this point no real way of knowing the big-picture importance of his discovery.
“My current intuition is that it might matter most for the redistribution of properties such as regional warming rather than for the total warming of the planet,” he said in an email.
“But that is purely intuition and we definitely need to study this more in order to give a proper answer to the question.”
Alaskans are, or should be, aware of the significance of regional warming coming off “The Blob” years. The Blob was the big pool of warm water in the southern Gulf of Alaska which has been blamed for over-cooking salmon runs, although it should probably be credited for boosting them over the long haul.
Through The Blob years, 49th state salmon harvests averaged over 200 million fish per year, a number unprecedented in human history, and the state enjoyed – except for diehard skiers and snowmachine riders – some of its warmest years.
University of Washington Atmospheric Science professor Cliff Mass, an authority on The Blob, doubts mesoscale turbulence would have much direct influence on The Blob.
“The Blob is mainly associated with changes in vertical mixing, not in horizontal mixing as discussed in this paper,” he said via email. “There aren’t strong gradients in the middle of The Blob.”
But The Blob clearly illustrates the influence of regional warming effects that might differ from or be associated with climate change.
The Blob roamed the western North Pacific Ocean from 2013 to 2018 with its hotspot usually centered somewhere in what might be considered an eddy in the North Pacific Gyre. Its warm water was implicated in everything from seabird die offs in Western Alaska to drought in California.
“…Nothing like it has been seen in the climate record since climatologists have been recording data in this region,” the National Park Service observed. “It is unprecedented in its magnitude (how warm and widespread) and its duration (to last multiple years).”
In that, it shares something in common with mesoscale turbulence. The Blob is, or least was for a time, a new player in a climate picture that just gets a little more complicated with every new discovery.
Buseke and Abernathy said they found “strong evidence that mixing rates in the ocean vary” widely across time and ocean regions to influence climate in as yet unknown ways.
If the mixing is helping the ocean capture and sequester carbon, it could theoretically moderate climate change. But if the mixing is causing the ocean to release more carbon, it could accelerate the build up of CO2 in the atmosphere.
“The observed mixing rates suggest a coupling between large-scale climate variability and eddy mixing rates due to small amplitude changes in the large-scale flow,” they wrote. “To our knowledge, such large-scale, coherent temporal variability between mesoscale mixing and global climates modes has not been documented before.”
They did agree with Mass’s observation as to the need to know more about the top-to-bottom mixing of ocean waters as opposed to the horizontal movements of water across the ocean’s surface.
A full assessment of the influences of mesoscale turbulence “will require more knowledge about the vertical structure of mixing rates,” they wrote.
The study comes at a time when climate has dealt some wild cards to scientists. A disruption in the polar vortex this week spilled frigid Arctic air into the American Midwest bringing record cold temperatures while it was raining in Alaska.
Climate scientist Judah Cohen at Atmospheric and Environmental Research (AER) admitted he was left scratching his head.
“The Arctic has been the ‘canary in the coal mine’ about the impacts of climate change with the greatest warming across the globe observed in the Arctic and the dramatic retreat of sea ice and even warm season snow cover recorded by satellites,” he wrote on the AER website this week. “The Arctic has warmed at least as twice as fast as any other region of the globe and the accelerating warming of the Arctic relative to the rest of the globe but especially the Northern Hemisphere mid-latitudes is known as Arctic amplification. The cause of Arctic amplification is surprisingly complex and not well understood but the cause is at least partially related to Arctic sea ice and snow cover melt. Certainly, heading into this winter, I was very confident that we would observe an anomalously warm Arctic this winter, especially coming off of last winter where the Arctic was record warm and sea ice was record low extent.”
Only that didn’t happen. The Arctic went cold last summer and stayed that way. An expected, record-low ice extent for September never materialized.
“Since then it has been at least strategically cold in regions across the Arctic this fall and winter that allowed sea ice to grow more extensive this winter in the Arctic basin compared to recent winters except in the Barents-Kara Seas,” Cohen observed. “But even more surprising to me has been how cold the Arctic has consistently been this winter, especially when compared to recent winters.”
Arctic sea ice did end the year at the third lowest extent in the satellite record that goes back to 1981, according to the U.S. National Snow & Ice Data Center, but it has since climbed to the fifth lowest on record.
The reason for the cool down is unclear, but oscillations in warming would not be unusual in a changing climate. Nothing in nature is linear.