Strange Times
There have been a lot of news stories and articles this summer about sightings of unusual marine life about our shores – hordes of jellyfish, giant basking sharks, weever fish, even a walrus for heaven’s sake. Eanna Ní Lámhna explains what’s happening.
More and more people – armed with mobile phone cameras- are spending their holidays around our coasts this year, rather than further afield as may have been their wont. Is that’s what’s causing so many strange sightings of maritime life? Or is there, in fact, an actual increase in these unusual sightings and if so, what is causing them?
Take the appearance of a walrus in our coastal waters over the past few months. Walruses live in the Arctic and sub-Arctic regions of the world near the North Pole. They are huge mammals – as big as cows, with both male and females having two large tusks. They feed on shellfish such as clams.
But actually there have been eight sightings of walruses in our waters since 1979 - and indeed the first recorded sighting was in 1897 in Valentia in Co Kerry. So can global warming be blamed for this? Nobody can say for definite why Wally the Walrus came here last March, but one theory is that an ice sheet he was sitting on in the Arctic Ocean broke off , floated south and finally melted completely, leaving the young walrus stranded, disorientated and a very long way indeed from home.
It certainly is true that global warming is causing a huge reduction in the amount of permanent ice on the Arctic Ocean around the North Pole.
In September, after summer warming, we see the lowest amount of permanent sea ice. In 1981 the extent of permanent sea ice was seven million square kilometres. It had dropped to six million by 2003, to five million by 2014 and in 2020 it was less than four million. Much less habitat therefore for species that depend on ice sheets, such as seals who haul out on it to give birth, polar bears who need it in order to catch their main prey- the seals - and walruses who use it to rest and breed on.
But what about all those jellyfish that frequented our bathing waters all summer? We are used to seeing the small common jellyfish that look like and are indeed the size of, fried eggs. But lots of very large Lion’s Mane jellyfish were seen too. But you know something? These actually are native to our waters and are here in the winter as well as in the summer. When these jellyfish are small and young, normally other fish would be eating them. But because of overfishing, there’s not enough fish to eat them and therefore many live much longer and become huge. They have very long tentacles that trail out in the water, and these can inflict really nasty stings on swimmers. But we can’t blame warming ocean currents for these – overfishing seems to be the cause.
But the ocean currents are warming as the seas themselves heat up, and these warmer currents are reaching our shores. This means that the plankton – tiny, microscopic plants and animals - bloom earlier in the year than they used to, because water temperature is very important to them. The giant basking sharks feed on these algae – they gulp in huge mouthfuls of sea water and filter the plankton out of them as food.
Because the blooms are happening earlier in the year now, the basking sharks feeding on them, are seen earlier than they used to be. But, actually, we are seeing more of them now, and they are bigger than they used to be because we have stopped hunting them for their oily livers. Oil used to be extracted from their livers for lamps in the 1800s. We have electricity now. If it all comes from renewable sources mostly wind, rather than fossil fuels such as gas, (and 43 per cent of our electricity in 2020 was from renewables) then we are striking a blow against global warming. So stop complaining about wind turbines.
What about rumours that the warm currents might be actually turned off by global warming – making Ireland a much colder country than it is now? Could that really happen? Well yes it could, if things go on the way they are going. We are at the same latitude as Labrador in Canada. They have six months of ice and snow every year and we complain if our temperature drops to minus two for two days in a row. We enjoy the benefit of the Gulf Stream that passes our shores on its way northwards from the tropics, while Labrador is washed by a cold returning current which sweeps back down from the Arctic.
This anticlockwise current in the Atlantic (the Gulf Stream) works at the moment, because hot salty sea water is lighter than cold salty sea water and so it rises to the surface of the ocean. This water is heated in the Gulf of Mexico and moves northwards along the west coast of Europe. When it gets up past Norway it naturally cools and sinks and this causes the Gulf stream to veer westwards and then southwards along the coast of Labrador. It is now very cold and so it causes the climate of Labrador to be much colder than ours.
However, if this current were to stop moving, we would get colder and Labrador would warm up. What would make it stop moving? Well fresh water is lighter than salt water. e ice sheet over Greenland is made up of fresh water and it is now melting very quickly, and the cold fresh water is fl owing into the ocean and sitting at the surface of the salt water. And this is slowing the Gulf Stream down and if it continues for long enough the Gulf Stream will stop altogether and we will get much colder. So maybe we should be glad to see the basking sharks appearing earlier each year.
Mind you we could do without the weever fi sh. ese nasty little fish used to occur in the warm waters of the Mediterranean and southern Europe. They are turning up now with ever more regularity on our beaches. They live buried in the sand just where the shallow waves meet the shore. They feed on the small plankton brought in by the tide. They defend themselves from predators with a sharp venomous spine that sticks up vertically from their backs and of course they are perfectly camouflaged, being the same colour as the sand. However, if an unwary barefooted swimmer happens to walk on one when entering or leaving the sea, the pain is terrible and can only be alleviated by bathing the foot in really, really hot water. I will bet there are not too many of them on the beaches in Labrador!