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.
(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.
(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.
(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.
Hat tip to Spike