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Signs of Gulf Stream Slowdown — Sea Level More Than a Foot Higher off US East Coast

It’s the stuff that climate disaster movies are made of. But the events are all too real — happening now and not part of some dramatized script played out on the silver screen.

Signs abound that global ocean circulation is being profoundly altered by human-forced climate change. A pool of cold water has developed in the North Atlantic. England is getting slammed by anomalous winter-type rains and gales in August. And sea surface heights off the US East Coast are more than 30 centimeters (one foot) above the 1979 to 2015 average.

Sea level anomalies 30 cm off US east coast

(Global sea surface height anomalies off the US East Coast are more than a foot (30 cm) above the 1979 to 2015 average. A clear sign that the Gulf Stream is slowing down, perhaps by as much as 15-30 percent. Complete shut down of the Gulf Stream, though unlikely without extremely large melt outflows from Greenland, would result in a very dangerous 1 meter sea level rise. An impact that is primarily driven by ocean current change. Sea level rise by thermal expansion and glacial melt would, necessarily, pile on top of this bulge of backed up waters. Image source: NOAA’s Climate Prediction Center.)

World Ocean Heartbeat Fading

This past March, after observations of rising sea levels off the US East Coast, extreme positive sea surface temperature anomalies in the same region, and a critical slowing down of North Atlantic over-turning recorded throughout the 20th Century, Professor Stefan Rahmstorf published this earth-shattering paper in the scientific journal Nature.

The paper meticulously recorded a slow-down of bottom water formation in a region of the Atlantic Ocean south of Greenland. The period studied included all of the 20th Century and the first one and one half decades of the 21st Century. Rahmstorf concluded that Greenland ice sheet melt — starting around 1900 and spiking after 1975 — was having a profound impact. Cold, fresh water issuing out from Greenland was cutting off the flow of heavier, salty water transported northward by the Gulf Stream. It was preventing larger portions of that water from sinking. And it was slowing down the Gulf Stream together with a host of other ocean circulation driving currents.

A system vital to both the life and health of the world ocean and global weather stability was entering an arrest. In other words, the world ocean heartbeat was fading.

The Gulf Stream Train Wreck

Since the publication of Rahmstorf’s paper, evidence of a bottom water formation interruption and a subsequent Gulf Stream train wreck continued to pile up. Sea surface temperatures off the US East Coast, during summer time spiked to as high as 85 Fahrenheit (29.3 C) off the coasts of New York and New Jersey. And regions off Nantucket hit as high as 80 degrees Fahrenheit (26 C). That’s between 7-10 F (4-6 C) hotter than average for an already typically warm Gulf Stream.

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(Left frame image shows Gulf Stream waters spiking to 29.3 C or 85 F off New York and New Jersey. Temperatures in the range of 7-10 F [4-6 C] above average. Right frame image shows cool pool development in the typical bottom water formation zone between Greenland, England and Newfoundland. Combined with the ocean current overlay, which shows widespread meandering, this hot south, cold north ocean surface dipole is an indication that the Gulf Stream is slowing down and that bottom water formation is weakening. Image source: Earth Nullschool.)

Further north, the opposite is happening. In the region east of the Grand Banks where the Gulf Stream currents typically flow strongly, there’s only a weak, meandering, confluence. The Gulf Stream appears to have hit a barrier. It has bottled up off the Northeastern US Coast. And it appears reluctant or unable to flow past mid-ocean.

As a result, a broad zone between England, the Southeastern Coast of Greenland and Newfoundland lack the warm, salty inflow of a strong Gulf Stream. Sea surface temperatures range from 2-7 F (1 to 4 C) below average. The northward progress of heat from the Gulf Stream is tapering off. And this cut off of heat flow from Equator to mid latitudes shows more and more as the development of an anomalous cool pool continues throughout.

Taking in the entire North Atlantic, what we see is a weather-destabilizing hot-cold dipole. The warm waters are backed up off the US East Coast. This is evidenced by both the very warm sea surface temperatures and by an extreme increase in sea surface heights by 1 foot over a broad region. And to the north, we have the climate change signature cool pool.

Anomalous Storms Strike England During Summer

This Gulf Stream train wreck and related cool pool development has already done a bit of a number on UK weather this summer. A series of gales and heavy rainstorms have slammed into the UK Coast — bringing heavy seas and torrential rains. One months worth of rainfall fell over parts of the UK during the past week alone. And with more storms on the way it appears that August of 2015 may be the wettest ever recorded.

It’s a changed climate state that Dr. James Hansen warned of in a recent paper. One that means more powerful storms for the North Atlantic as the Greenland Ice Sheet spews out greater and greater volumes of water and ice. Ever since 2012, we’ve seen a tendency for these kinds of anomalously powerful storms. And more rough weather is certainly on the way.

storms-reshape-englands-coastline

(During the winter of 2013 and 2014, storms reshaped the coastlines of the British Isles. But this was just the start. For the North Atlantic is now in the process of firing up an age of storms. Image source: AGU.)

The Fall forecast is calling for the strong gales that we’ve already seen to continue to intensify through at least October and November. Strong storms that will draw energy by the high differences in sea surface temperatures in the North Atlantic, but also, possibly, from an El Nino-amplified storm track causing powerful troughs to begin to dig in off the US East Coast. A situation that could set up a kind of trans-Atlantic storm firing line.

The long term forecast, however, is even worse. With Greenland just beginning to shed more and more of its ice, the cool pool off England will tend to intensify even as the hot pool off the US East Coast and within the Gulf of Mexico heightens. A screaming, storm-generating temperature differential that such melt will worsen as the decades wear on and if human fossil fuel burning continues to add more heat fuel to this already developing dangerous situation.

Links:

NOAA’s Climate Prediction Center

Rahmstorf– AMOC is Slowing Down

World Ocean Heartbeat is Fading

Earth Nullschool

Even Chances August Will Be Wettest on Record for The UK

Warning From Scientists — Halt Fossil Fuel Burning or Age of Storms, Rapid Sea Level Rise is Coming

North Atlantic Ramping up to “Storms of My Grandchildren?”

AGU

Fall Forecast: Storms Target UK, France

Hat tip to Spike

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Bermuda High No More — Global Warming Shoves North Atlantic Anticyclone Toward Azores

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.

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(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.

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(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.

Links:

Semi-Permanent Weather Patterns

Earth Nullschool

Global Forecast System Model

Hadley Cell

Ridiculously Resilient Ridge

Terribly Tenacious Trough

Warning From Scientists: Stop Fossil Fuel Burning or Age of Storms, Rapid Sea Level Rise is Coming Soon

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