Increasing ocean stratification over the past half-century

[bdgwx]

Yet another study with significant implications. 

Official: Li et al 2020: Increasing ocean stratification over the past half-century

Open access: use this link

News article: Mixing of the planet’s ocean waters is slowing down, speeding up global warming, study finds, Washington Post, September 29, 2020

Abstract: Seawater generally forms stratified layers with lighter waters near the surface and denser waters at greater depth. This stable configuration acts as a barrier to water mixing that impacts the efficiency of vertical exchanges of heat, carbon, oxygen and other constituents. Previous quantification of stratification change has been limited to simple differencing of surface and 200-m depth changes and has neglected the spatial complexity of ocean density change. Here, we quantify changes in ocean stratification down to depths of 2,000 m using the squared buoyancy frequency N2 and newly available ocean temperature/salinity observations. We find that stratification globally has increased by a substantial 5.3% [5.0%, 5.8%] in recent decades (1960–2018) (the confidence interval is 5–95%); a rate of 0.90% per decade. Most of the increase (~71%) occurred in the upper 200 m of the ocean and resulted largely (>90%) from temperature changes, although salinity changes play an important role locally.

This finding has a few implications.

• Reduced heat transport into the ocean depths means more heat is available to drive atmospheric temperatures upward.
• The faster warming of the ocean surface will reduce carbon uptake since uptake is inversely proportion to the ocean temperature thus resulting in less carbon buffering and an increase in the rate at which CO2 is accumulating in the atmosphere.
• The rate at which additional energy is becoming available to tropical cyclones is increasing.
• The increased stratification may disrupt the Atlantic Meridional Overturning Circulation causing it to slow down.

 

[donsutherland1]

3 hours ago, bdgwx said:

Yet another study with significant implications. 

Official: Li et al 2020: Increasing ocean stratification over the past half-century

Open access: use this link

News article: Mixing of the planet’s ocean waters is slowing down, speeding up global warming, study finds, Washington Post, September 29, 2020

Abstract: Seawater generally forms stratified layers with lighter waters near the surface and denser waters at greater depth. This stable configuration acts as a barrier to water mixing that impacts the efficiency of vertical exchanges of heat, carbon, oxygen and other constituents. Previous quantification of stratification change has been limited to simple differencing of surface and 200-m depth changes and has neglected the spatial complexity of ocean density change. Here, we quantify changes in ocean stratification down to depths of 2,000 m using the squared buoyancy frequency N2 and newly available ocean temperature/salinity observations. We find that stratification globally has increased by a substantial 5.3% [5.0%, 5.8%] in recent decades (1960–2018) (the confidence interval is 5–95%); a rate of 0.90% per decade. Most of the increase (~71%) occurred in the upper 200 m of the ocean and resulted largely (>90%) from temperature changes, although salinity changes play an important role locally.

This finding has a few implications.

• Reduced heat transport into the ocean depths means more heat is available to drive atmospheric temperatures upward.
• The faster warming of the ocean surface will reduce carbon uptake since uptake is inversely proportion to the ocean temperature thus resulting in less carbon buffering and an increase in the rate at which CO2 is accumulating in the atmosphere.
• The rate at which additional energy is becoming available to tropical cyclones is increasing.
• The increased stratification may disrupt the Atlantic Meridional Overturning Circulation causing it to slow down.

 

This is a disturbing development. It will likely amplify the changes being driven by AGW. 

[Bhs1975]

There’s a lot we still don’t understand like these feedbacks that will make the situation worse.

[LibertyBell]

On 10/2/2020 at 8:04 PM, donsutherland1 said:

This is a disturbing development. It will likely amplify the changes being driven by AGW. 

slower jet stream and slower gulf stream too?