Antarctic ice melt will have the minimal impact of delaying atmospheric warming by a decade and a half but will raise sea levels rapidly and change precipitation patterns worldwide “because the tropical rain belt will shift north” according to new research published in the journal Nature. The increasing rate of meltwater will significantly alter climate projections. It is the first newly identified feedback loop in 20 years according to senior author Joellen Russell.
Ugh.
The new study came out recently, it was funded by NOAA, with data provided by the Geophysical Fluid Dynamics Laboratory, the University of Arizona led the research.
I was stunned to see that NOAA’s climate.gov web page showed up in my google search because as you know, the Trump regime has been furiously removing science from government websites since day one. It appears the source datasets were scrubbed by the fossil fuel interests that Trump embedded in those agencies tasked with protecting the environment. GFDL is an NOAA laboratory located at Princeton University. Check the dead link yourself here.
There is a second story below the fold that ties Greenland and Antarctica changes together.
From the study abstract:
Melting is pervasive along the ice surrounding Antarctica. On the surface of the grounded ice sheet and floating ice shelves, extensive networks of lakes, streams and rivers both store and transport water. As melting increases with a warming climate, the surface hydrology of Antarctica in some regions could resemble Greenland’s present-day ablation and percolation zones. Drawing on observations of widespread surface water in Antarctica and decades of study in Greenland, we consider three modes by which meltwater could impact Antarctic mass balance: increased runoff, meltwater injection to the bed and meltwater-induced ice-shelf fracture — all of which may contribute to future ice-sheet mass loss from Antarctica.
It’s important to note that the speed up of marine ice cliff collapse we have witnessed is caused by the warming of the southern ocean due to relentless burning of fossil fuels, and not by meltwater fracture, at least not yet. It is believed that the Larsen B breakup was caused by hydrofracture.
From the University of Arizona press release.
Observations show that the Antarctic ice sheet has been melting faster in recent years.
The UA-led team found that by the year 2100, sea level could rise as much as 10 inches more than the previous estimate of approximately 30 inches by 2100.
To figure out whether the melting of the Antarctic ice sheet would affect global climate, the research team modified one of the most current climate computer models to include the ice melt.
Adding the melted ice into the team’s model indicated that the global temperature would increase by 2 degrees C (3.6 F) by the year 2065, rather than the year 2053, the team writes.
In addition to slowing warming and increasing sea level, the melting of the Antarctic ice sheet will change precipitation regimes because the tropical rain belt will shift north, said senior author Joellen Russell, who holds the Thomas R. Brown Distinguished Chair of Integrative Science and is an associate professor of geosciences at the UA.
"Our projections indicate the tropical rain belt will shift toward the Northern Hemisphere, making it slightly wetter in the Northern Hemisphere and slightly drier in the Southern Hemisphere than previously predicted," Russell said.
NOAA writes:
Ice sheet melt is a known neglected forcing in climate model simulations, contributing to uncertainties in climate projections. This is the first study to directly implement estimates of Antarctic ice sheet melt in a climate simulation, showing the actual change in climate projections due to the freshwater input. The authors used a large ensemble to confidently separate the freshwater signal from natural variability and show when we can expect these freshwater-induced effects to become significant.
The study shows that adding Antarctic ice sheet melt estimates to GFDL’s Earth System Model (ESM2M) significantly alters future climate projections. The addition of ice sheet melt to a 21st century climate projection reduces global warming. However, this comes at the more significant cost of potential increased future sea level rise through increased ocean warming. We also show that the ice sheet melt causes more precipitation just north of the equator, and less precipitation south of the equator, due to a Northwards shift in the Inter-tropical convergence zone. This means reduced future drying in areas like Central America, but increased drying in Australia. The authors propose that the freshwater input associated with the ice melt should be included in all future climate simulations to improve 21st century projections.
Observations over the satellite era show a positive trend in Southern Ocean sea ice cover. This observed trend can be simulated without ice sheet melt through natural variability, but it is far more likely to occur in climate model experiments, in a scenario with ice melt. The ice sheet melt also causes sea ice expansion until the middle of the century, suggesting that the observed trend is also likely the beginning of a longer trend.
Speaking of central America. Increased migration from these areas is linked to climate change. The president should take note.
Violence in Honduras, Guatemala, and El Salvador—three of the countries where most recent asylum seekers are coming from—is the immediate cause for people to up and leave. But as with Syria, a widespread drought that devastated farmers in Central America’s Dry Corridor has helped destabilize the region. Coffee rust—a fungus that can kill coffee plants and thrives in warmer temperatures—has affected 70 percent of Central America’s coffee farms and caused 1.7 million workers to lose their jobs.
The signs of how climate shifts are already influencing migration, coupled with a report by federal scientists warning the risks of migration and instability will only grow in a warming world would, in a rational world, lead a government to consider how to mitigate these risks. But rather than listening to the red alerts, the Trump administration has doubled down on policies that will drive carbon pollution higher. The president himself has flatly said he doesn’t believe the report.
Past warming events in the Arctic linked to shifting winds in the Antarctic
The Antarctic ice core shows that Southern Ocean winds shifted at the same time, or at most within a few decades, of each rapid Greenland warming event. Antarctic air temperatures, on the other hand, are connected through the slower-moving oceans and took about two centuries to respond.
Co-author Eric Steig, a UW professor of Earth and space sciences said: What we found is that when it warms up abruptly in the Northern Hemisphere, the winds in the Southern Hemisphere move north, and blows over warmer water. And the opposite happens when it cools down quickly in the north: the winds shift south.
It was already well known that tropical rain bands and the Northern Hemisphere jet stream adjust to the temperature balance between hemispheres. But there was little historical evidence for winds blowing over the icy southern seas.
The new study uses chemical clues in the 70-thousand-year ice core rec seawater, the fraction of heavier to lighter hydrogen and oxygen atoms in vapor depend on the ocean's temperature. When this moisture eventually falls as snow over Antarctica, it contains a signature of the latitude where it evaporated.
Results show that the winds shifted north toward the equator when Greenland warmed, through a signal that was communicated through the atmosphere.
When it warms up rapidly in the Northern Hemisphere it creates strong temperature gradients, whi influence the rain belts in the tropics. The rain belts in the tropics affect where the winds blow in the Southern Hemisphere. So it's a chain of effects, Steig said.
Besides being important for Antarctic climate, the Southern Ocean winds influence rainfall in S America, Australia and southern Africa. These winds also play a role in long involve Antarctic sea ice and the uptake of atmospheric carbon dioxide by the oceans.
While there is some evidence that Southern Ocean winds may be changing today, the causes would be different from those in the study, the authors cautioned. But the results establish a new bridge between the two hemispheres, and support the results from computer models that create detailed simulations of the global climate over thousands of years.
Resist!
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