Glass Eels and the Gulf Stream

It is mid-May and snow has fallen to a depth of 2 ins down in the south west of England. Here it is -5 degrees centigrade. The swallows called one day when it was warm, earlier in the month, but mostly it is cold, often wet, and at the moment the rain falls as hail. Three years ago we used to see about 100 minimum chaffinches pecking the ground around the cottage; this year I have counted 10 at the most together. A small tortoiseshell butterfly emerged from its hibernation in April, flew out on a warmish day, but unlikely to have survived the ensuing wintery weather. On the warm day in May when a few swallows arrived, a large white butterfly emerged and fluttered around my cottage garden. Again, wintery weather followed and I hope it found somewhere to hide. So, we in the UK are always talking about the weather patterns, and how they have changed over the past 5 years.

I was reading the Colorado National Snow & Ice Data Centre website today.

It makes grim reading for those of us living in the northern hemisphere, in Europe and North America. The focus is on the Arctic ice which is now measured with satellite instruments. It is this time of year when readings are so important. The summer annual melt season usually begins in March. It ends in September. By October the sea ice minimum will be known. But the melt season is taking longer now and consequently the interaction of ice with the Earth’s global systems are effectively changed. The wintering process should begin in October and by March there should have been sea ice recovery, but this is in decline. It is 80 percent less than it was 30 years ago. As the Arctic is land based and the Antarctic is sea based, each area impacts on the global climate in different ways. Arctic changes in ice cover continue to show extreme weather in mid latitudes with a record sea ice melt in September 2012. This impacts on the jet stream (which earlier blogs have covered regarding the weather changes). Huge areas of normally frozen ocean have prevented the sun’s rays being reflected back into space (the albedo effect), thus more ice melts and there is a momentum now which is likely to damage the permafrost deep down. The wind patterns are changed with the atmospheric disruption and the sea will likely surge more often, leading to storms. In the next years of my life I can expect to hear of record heat, rainfall, drought and floods in the northern hemisphere.

With that in mind, I am not surprised at the cold temperatures here in May.

14th to 15th May – 2 inches of snow fell in Shropshire and that area plus Wales received 3 inches of rain within 24hrs. According to weather forecaster, Philip Avery

“It’s unusual but not unheard of to have snow in May.

If you go back to 1955, 17 May, snow fell widely across England and Wales.

In May 1968 snow fell as far south as the Midlands.

Snow again was confined to the higher ground in 1979, 1981 and 1982 in May.

May 1993 saw several centimetres in central Britain on higher ground.

We have had instances of snow falling as late as June, such as 1975, and there was a sleet shower reported at Birmingham Airport in June 1985.”

An item on the news today about a massive glut of glass eels (Eel Anguilla anguilla; Linnaeus, 1758. Family: Anguillidae) surprising everyone as they arrived into the River Severn. The item was more about eating them as a delicacy though. This was reflected in the Daily Mail headlines:

“Baby eels squirm their way back onto British menus after the biggest harvest in 30 years drops prices

* Elver eel numbers could reach 100million this year – ten times last year
* Fishermen say it is the largest harvest they’ve seen in 30 years
* This has meant restaurants can serve the delicacy at reduced prices”

European eels have a fascinating life cycle, spawned as larvae in the Sargasso Sea (the western part of the subtropical gyre of the North Atlantic Ocean between Bermuda and the Azores, a region of the Bermuda Triangle) before travelling with the Gulf Stream to Europe, developing into glass eels. No one has witnessed an adult eel spawning in the ocean, yet that is where it all happens, in a mysterious and wondrous way. A single eel can unleash 30,000 eggs. She releases her eggs and dies. Only very fine nets of factory ships have evidenced this occurrence after hauling the newly hatched offspring in whilst working in the ocean. They distribute themselves evenly as they migrate to coastal areas and move from salt water to freshwater for the next phase of their life cycle.

In Scotland, eels can be found in all types of water body, including both upland and lowland, flowing water and still, and productive and unproductive waters, although they probably prefer rich, muddy, slow-flowing environments. The eel has a varied diet in fresh waters, feeding habits varying with size and location. Smaller animals tend to feed on vertebrates; larger animals take an increasingly large proportion of fish. Little food is taken in winter. Since the eel grows very slowly in the cool, nutrient-poor waters of Scotland, populations are highly vulnerable to over-exploitation. Consequently there is little tradition of fishing for adult eels in Scotland.

Back in 2008, it was reported :

Groundbreaking project saves glass eels

They’re one of the most endangered species on the planet, but now work on the River Parrett could safeguard their future. Special ‘eel passes’ have been built to help them swim upstream to fresh water.” Why were they endangered? Part of the reason has been hydropower dams that macerate them on their downstream migrations, to coastal and river development that destroys or degrades their habitat, and to fisheries working to satisfy a robust demand for eels in Asia, especially in Japan. (http://e360.yale.edu/feature/a_steady_steep_decline_for_the_lowly_uncharismatic_eel/2316/)

But now, in May 2013:

The Daily Mail goes on to report:

………. that the numbers caught this year could be enough to keep rivers healthily stocked with eels for six to 10 years.

So far, 660,000 Severn elvers have been donated for re-stocking rivers in this country and that figure will rise at the end of the season, he said.

The elvers need to be taken out of the Severn and relocated because flood barriers are now so effective that they would be unable to reach other streams and tributaries and would perish.

Andrew Kerr, former chairman of Gloucestershire Wildlife Trust and now chairman of the Sustainable Eel Group, said ‘It is just extraordinary how many elvers there have been in the Severn this season.’

He said the precise reasons why there are shortages some years and gluts others cannot be explained.

But the variation of currents in the Atlantic as the elvers are swept from the Sargasso Sea to the Severn could be part of the reason.

‘They migrate with the tide and they come up the river in waves. There have been tales this year of fifty mile streams of elvers,’ he said.”

Nobody can explain (yet) why so many have arrived, and wonder if the changes in the Gulf Stream could be the cause. So I thought I would become more educated on the latest scientific research about the Gulf Stream )

The rise in temperature of North Atlantic waters and the decreasing salinity over the past decades, has increased the supply of freshwater into Arctic seas. The salinity of seawater is usually 35 parts per thousand. The most important components of seawater that influence life forms are salinity, temperature, dissolved gases (mostly oxygen and carbon dioxide), nutrients, and pH. pH is a measure of the acidity or alkalinity of a substance and is one of the stable measurements in seawater.

Temperature matters. If any ocean species is moved out of its temperature tolerance range it may die in a short time although temperatures on the cool side of the range are easier for organisms to tolerate than temperatures on the warm side because cell reactions just slow down in the cold but may speed up over six times the normal levels for each 10 degrees C of heat. (http://www.marinebio.net/marinescience/02ocean/swcomposition.htm)

Global warming has resulted in an increase in ocean temperature and this may well have had an impact on the Gulf Stream. The Gulf Stream when off Florida, moves water at 85 million cubic meters per second from the Caribbean Sea. It then moves toward high altitudes via the eastern coastlines of the USA northward and then, south of Newfoundland, the cold Labrador Current slows it down to 8 km a day and reduces its temperature to 25 centigrade. It then changes direction and flows north-eastward through the Atlantic Ocean (known as the ‘North Atlantic Drift’).

The Gulf Stream plays a part, but only contributes 20 percent of the warmer air to Europe. The ocean stores heat in the summer and releases it in the winter and 80 percent of the heat transfer is created by the dominant Western winds coming from the United States blowing over the Atlantic ocean as it releases warmth and brings oceanic air to Europe. On arrival in Europe it divides in two with the northern stream flowing towards Iceland, the southern stream towards the Azores in the direction of the Canaries. This is the ‘conveyor belt style’ system which causes colder water to sink and stream toward the Equator. When the water moves to the Polar regions, it has, in the past, evaporated and transferred heat to the atmosphere. The oceans have frozen, trapping carbon dioxide for hundreds of years, sinking to a depth of more than 3km along “convection chimneys”.

When large water masses with different densities meet the denser water mass slips under the less dense mass. These responses to density are the reason for some of the deep ocean circulation models, such as the Gulf Stream.

Fact: the colder and saltier the water is the denser it is. The pH of the ocean is determined by the level of hydrogen protons (H+) in sea water. The lower the pH, the more acidic the ocean. Co2 is no longer trapped in ice, instead higher levels of CO2 remain in the atmosphere which in turn push up the rate of global warming- and that heats the oceans and prevents ice forming. Instead freshwater surges in to the ocean denying the salinity necessary to retain the density required to help water sink, the pH levels have lowered, thus increasing the acidification. Global weather patterns continue to change as a result..

CO2 peaks in May every year. Atmospheric concentration of carbon dioxide has been rapidly increasing in the last 250 years from the pre-industrial 280 ppm to 400 ppm measured this month. It takes about a year for northern pollution to spread through the Southern Hemisphere to reach the measuring instrument perched on a high mountain in Hawaii, the Mauna Loa. Mauna Loa lags the Arctic, where CO2 levels are higher. A year ago, NOAA reported that the average of its Arctic measurements had exceeded 400 ppm for the entire month of May, not just for a single day. By 2015 or 2016, the whole atmosphere will be averaging 400 ppm for the whole year.

During the Pliocene Epoch, 3 million years ago, greenhouse gas reached this mark, horses and camels lived in the high Arctic. Seas were at least 30 feet higher—at a level that today would inundate major cities around the world. But tens of millions of years ago, CO2 must have been much higher than it is now—there’s no other way to explain how warm the Earth was then. In the Eocene, some 50 million years ago, there were alligators and tapirs on Ellesmere Island, which lies off northern Greenland in the Canadian Arctic. They were living in swampy forests like those in the southeastern United States today. CO2 may have been anywhere from two to ten times higher in the Eocene than it is today. Over the next 45 million years, most of it was converted to marine limestone, as CO2-laden rains dissolved the ingredients of limestone out of rocks on land and washed them down rivers to the sea. CO2-belching volcanoes failed to keep pace, so the atmospheric level of the gas slowly declined. Some time during the Pliocene, it probably crossed the 400 ppm mark, as it’s doing now-but back then it was on its way down. As a result, at the end of the Pliocene, it became cold enough for continental ice sheets to start forming in the northern hemisphere. “The Pliocene”, says geologist Maureen Raymo of Columbia University’s Lamont-Doherty Earth Observatory, “was the last gasp of warmth before the slow slide into the Ice Ages.”

Whilst we continue to shiver mid May, with snow on the crop growing fields of Shropshire, one thing we can be sure of in the coming years: plenty of shocks and surprises as Mother Nature ticks us off for our misdeeds to the Planet.

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About borderslynn

Retired, living in the Scottish Borders after living most of my life in cities in England. I can now indulge my interest in all aspects of living close to nature in a wild landscape. I live on what was once the Iapetus Ocean which took millions of years to travel from the Southern Hemisphere to here in the Northern Hemisphere. That set me thinking and questioning and seeking answers.
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