The semi-permanent weather patterns are all out of whack. The Aleutians Low has been shoved into Alaska and the Beaufort. The Pacific California High has shifted north and west to dominate the region previously claimed by the Aleutians Low. And the Bermuda High — a feature famous for directing tropical cyclones northward along the Atlantic Seaboard has packed its bags and fled north and east.
During the late summers of more stable climates, a strong high pressure system tended to form over the region of Bermuda. The high swept warm, moist air up off the Atlantic Ocean and over the Eastern Seaboard of the United States. The high was also a reliable governor of the movements of tropical cyclones — with the position of the high critical in determining whether these powerful summer storms would make landfall or rocket out to sea.
But this August, the Bermuda High is nowhere to be seen. Instead, it’s shifted more toward mid and north Ocean — closer to the Azores and the Flemish Cap.
(The Bermuda High can now also be counted among the growing number of climate change refugees as it emigrates to the Azores and the higher Latitudes of the North Atlantic. Image source: Earth Nullschool.)
In the above image, provided by Earth Nullschool, white denotes areas of high pressure and purple-to-red denotes areas of low pressure. The green circle in the image marks the position of the North Atlantic High in today’s GFS summary map. Note that the high is shifted more than 1,000 miles to the east and north. It sits at the base of a ridge that stretches well north of the Flemish Cap and then extends eastward to just south of Britain, Scotland and Ireland. Near Iceland, a powerful cyclone rages. A fickle storm that alternatively sets its sights along an arc from England to Svalbard.
How Human-Caused Warming Shoves the Bermuda High Northward
A semi-permanent high pressure system north of the Azores and a very stormy North Atlantic in the triangle between Greenland, Svalbard and England is not remotely a normal summer weather pattern. It’s instead a feature of a number of new ocean and atmospheric dynamics that are the upshot of human-caused climate change.
As equatorial heat embodied by the Hadley Cell expands outward from the lower Latitudes, the oceanic highs, including the Bermuda High, are shoved northward. This motion tends to also shift weather tracks into higher Latitude boundaries even as it, at first, enhances waviness in the Jet Stream. Near North America, we can see this dramatic weather alteration in the form of the Ridiculously Resilient Ridge over the Pacific and the Terribly Tenacious Trough over the Eastern Seaboard.
A second feature that influences the displacement of the North Atlantic High is the expansion of a cool pool of water to the south and east of Greenland. This cool pool is an upshot of the ongoing melt of the Great Greenland ice sheet. As fresh water spills out from Greenland’s glaciers it cuts off the northward propagation of the Gulf Stream even as it prevents bottom water formation. This shutting down of ocean circulation causes heat to build further south along the Eastern Seaboard of the United States and in the Caribbean and Gulf of Mexico. The lack of south to north heat transport combines with the expanding fresh water cap to prevent ocean heat ventilation at the surface in the North Atlantic. As a result, we see an expanding pool of cool water in this zone. A signature feature of both human caused climate change and of glacial melt in Greenland.
(Earth Nullschool temperature anomaly map focused in on the North Atlantic with near -5 C readings in an uncanny and freakish cool pool there. This is the mirror opposite of the Hot Blob in the Northeast Pacific. And, eerily enough, it is also a feature of overall global warming. Image source: Earth Nullschool.)
During recent years, we have seen more and more of this cool pool formation as both the Gulf Stream and bottom water formation in the North Atlantic slowed down due to fresh water outflows from Greenland. It’s an oceanic cool pool that forms a kind of atmospheric slot for the Bermuda High to slip north through. It also generates an unstable boundary zone between hot and cold waters and airs — a mechanism that generates very high potential energies for powerful storms cycling in a rough arc around Greenland (climate change driven storms of this kind were the subject of a recent paper by Dr. James Hansen.)
As glacial outflows from Greenland expand due to a continued forced economic dependence on fossil fuels and the dumping of their toxic, heat-trapping emissions into the atmosphere, we are likely to see the Bermuda High continue to shift north. It’s the first of many features that will tend to produce powerful atmospheric bomb-type storms in a great zone within the North Atlantic. Storms of an intensity we likely haven’t seen through all the 10,000 year period of the Holocene.
It is for this reason that the shift of the Bermuda High north and east should be viewed as an ominous atmospheric move. One that is preparatory to far worse weather to come — during a time when the old Bermuda High will, perhaps, be viewed with a kind of fond nostalgia. A gentler weather feature of a once far kinder climate.