Ocean hot spots could help today’s long-range weather forecasters predict extreme summers for Central US
From the University of New South Wales, this reminds me of the recent issue over the “warm blob” in the Pacific which is strengthening and the current drought situation in the USA. A video follows.
Credit: NOAA George E Marsh Album
Two ocean hot spots have been found to be the potential drivers of the hottest summers on record for the Central US in 1934 and 1936. The research may also help modern forecasters predict particularly hot summers over the central United States many months out.
The unusually hot summers of 1934/36 broke heat records that still stand today. They were part of the devastating dust bowl decade in the US when massive dust storms travelled as far as New York, Boston and Atlanta and silt covered the decks of ships 450km off the east coast.
Research by Dr Markus Donat from the ARC Centre of Excellence for Climate System Science and colleagues has revealed that unusually warm sea surface temperatures occurring at exactly the same time in two very specific locations were likely responsible for creating the record breaking heat.
“In the Pacific, there were anomalously warm ocean temperatures along the coastline of the Gulf of Alaska stretching down as far as Los Angeles,” said Dr Donat.
“On the other side of the country in the Atlantic Ocean, in a relatively small area off the coast of Maine and Nova Scotia, the ocean surface was also unusually warm. Together they reduced spring rainfall and created perfect conditions for scorching hot temperatures to develop in the heart of the US.”
As part of their study, the researchers compared the large-scale climate conditions in 1934 and 1936 with those of the extensive recent hot drought years of 2011 and 2012 to see if there were any similarities to the dust bowl years.
They found that in 2011 / 2012 while there were definitely warm ocean temperatures off the coast of Nova Scotia and Maine, the same was not true along the coastline of the Gulf of Alaska, where ocean temperatures were below normal.
“The large scale ocean conditions in 2011 and 2012 were very different from 1934 and 1936, suggesting an event of a quite different nature,” Dr Donat said.
“Only very rarely have we seen these very specific ocean regions warm at the same time over the past century, but those combined warm anomalies were never as strong as during the two record breaking years of 1934 and 1936.”
This unusual ocean warming in two regions compounded the impacts on the atmosphere and pressure gradients across the continental US, profoundly changing the weather systems during the spring and summers.
The Atlantic warming off Nova Scotia and Maine meant southerly winds shifted further north-east and the transport of moist air from the Gulf of Mexico northward into the Central US was weakened. At the same time, the Pacific Ocean warming expanded a large Pacific high that also contributed to reduced transport of moist air into the central US.
“Not only did the warming amplify summer temperatures, it also reduced spring rainfall,” Dr Donat said.
“To make matter worse, past research has shown the atmospheric dust over Western North America once summer was underway had a positive feedback that intensified the high pressure system even further.”
“The US has been very fortunate that it has not seen a repeat of this coincident ocean warming at such a level. Should this ocean warming reoccur in exactly the same constellation, because of climate change it is likely the temperature impacts would be even more devastating and those old records may be surpassed.”
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Video explaining the research:
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pyeatte May 4, 2015 at 7:30 am
One thing about the Dust Bowl. There was a natural, cyclical ~30-year drought, but the “Dust” part was human caused. Under US Government policies, the great prairie grasslands were plowed up for crops. The grasslands had very deep root systems that would hold the ground (dirt) in place in the face of dry winds while the grass would also lay flat covering the ground. The crops that replaced the grass would leave the dry land bare with no protection, hence the endless dust storms.
Repeated for effect. Stubble burning was rampant at the time as well, which turbo charged the whole mess. Low till, zero till, stubble left on fields to keep soil in place as well as capture drifting snow for early moisture in fields, planting of wind breaks…. long list of things that will make the next big drought period rather different from the dirty 30’s.
That said, I haven’t read the paper, but I see no mention of a causal link. Just correlation? Based on data acquired by ships throwing buckets overboard and hauling them up to take the temperature. Limited accuracy by sampling method, limited accuracy by instrumentation, and limited accuracy in terms of location. Don’t know if I trust the correlation, and if I had all the data, I bet I could find two or three areas of the ocean that were anomalously cold at that exact point in time (its always warmer somewhere and colder somewhere than usual on this planet of ours) so without a causal link, its just correlation.
Key role of the Atlantic Multidecadal Oscillation in 20th century
drought and wet periods over the Great Plains:
http://www.atmos.umd.edu/~nigam/GRL.AMO.Droughts.August.26.2011.pdf
I think that the Blob will not be with us for much longer. Several weeks ago I mentioned that an intrusion of cooler waters was workings it,s way through the middle of the Blob …
goldminor
April 21, 2015 at 1:46 pm
I have been watching this for some time, also. I noticed that at the beginning of this month that there were cool inroads being made into the center of the Blob….http://wattsupwiththat.com/2015/04/21/north-pacific-update-the-blobs-strengthening-suggests-its-not-ready-to-depart/#comment-1913298
Since the above comment was made the ssta has changed considerably, a bit faster than I thought it would. I was thinking that by July it would be mostly gone, but that could take place somewhat quicker at the current rate of change.
“unusually warm sea surface temperatures occurring at exactly the same time in two very specific locations were likely responsible for creating the record breaking heat“. One event, no mechanism, and when they compare with 2011-12 they find something different. OK, it’s interesting that there were two areas of warm sea at the time of the dust bowl, but without anything more it is a step too far to claim any connection. As others have pointed out, there were some farming practices that exacerbated the drought.
I think that oceans are a great barometer for our planet and that it’s extremely important to keep an eye on them and to be attentive in which way we do influence them. The oceans affected by naval and merchant ships operating and sailing the seas back and forth should have been the hottest topic in the debate on climate change since meteorology was established as a science in the late 19th century. Instead of that, oceans were ignored up to the late 20th century and not even today do they enjoy the significant position they deserve. Oceans are a decisive climatic force, the second after the sun.I emphasize with the idea that Naval War had a great impact in the climate change. I suggest visiting http://www.1ocean-1climate.com, you’ll find information that will sustain my idea.
The warm spots in the two oceans are unrelated and most likely have nothing to do with the Dust Bowl. The warm spot in the Atlantic is related to the sudden increase of Arctic warming at the begiinning of the twentieth century (see my paper in E&E),. Prior to that there was nothing in the Arctic but slow, linear cooling for two thousand years. The warming was caused by a change in the North Arlantic current system that started to carry warm Gulf Stream water into the high Arctic. The warm spot in the Atlantic is related to this diversion of the Gulf Stream flow to the north. This phase of Arctic warming ended in 1940 and was followed by thirty years of cooling. Warming resumed in 1970 and is still going on. I attribute the Blob in the Pacific to highly unusual wind patterns involving a strengthening and diversion of the westerlies which then hijacked the warm water of the Indo-Pacific Warm Pool, pushed it across the ocean, and puddled it up against the coast of the Gulf of Alaska, Canada, and our northwest states. It is apparently a rare occurrence that we should not expect to see again for quite a while.