Images

Supertides in Scotland

By Dr Jason McIlvenny and Dr Philip Gillibrand, Environmental Research Institute, North Highland College UHI

Background

The tides around the coast of the United Kingdom fluctuate between “spring” tides and “neap” tides according to the moon’s phase, full moons and new moons giving rise to the largest range tides, known as “spring” tides. That means that both the highest high tides and the lowest low tides (i.e. the largest range) occur at “springs”, while at neap tides the tidal range is smallest. The word “neap” is thought to have originated from the Middle English word ‘neep’ meaning small.  The word spring refers to the tide springing up and not the season of spring.

In simple terms, spring tides occur when the gravitational effects of the moon and the sun are aligned, giving the greatest net effect. At neap tides, the gravitational pull of the sun and the moon act in perpendicular directions, so the net effect is smaller.

There are other, more subtle, effects on the tides, due to slow variations in the relative orbits of the earth, moon and sun. For example, due to the tilt of the earth and orbital changes, there is an astronomical tidal cycle with an 18.6 year period (known as the ‘nodal period’). During 2015 we will reach the peak of this cycle. Therefore at springs, the large tidal range will be even larger with higher than normal high tides, leading to the so-called supertides. The largest tides will occur at the spring and autumnal equinoxes:

  • 20-21 February 2015
  • 29-30 September 2015

Tides at the equinoxes are generally the largest of the year, so this year will be the largest seen for a number of years.

Risk

The high astronomical tides will not cause coastal flooding alone around the Scottish coastline unless combined with the effects of storm conditions. Storm systems can cause an increase in water level known as a storm surge which can elevate the normal tidal height as much as 1.5 meters.

In contrast to this, the upcoming astronomical tides will increase the average spring tide height up to 30 cm around Scotland (most places however will be increased only 10 to 20 centimetres).  The difference in tides between locations depends on local conditions such as the shoreline topography and contour of the ocean floor.

At Scrabster, for example, an average spring tide consists of a high water of approximately just over 5 meters and a low water of approximately 0.5 m. The super tide in January increased this tidal ‘range’, with a high water level of 5.3 m and a low of 0.2 m. It might not sound much (increase of ~25 cm on normal tidal levels); however, if combined with a storm surge there is an increased risk of coastal flooding.

In Inverness the super-tide for January caused a predicted high tide of 5.0 m and a low tide of 0.7 m, whereas an average spring tide (for example, on 22 December 2014) the high water mark was 4.7m and the low tide was 0.9m).

Some tidal statistics from around Scotland are given in the table below:

Location Area HighestTide 2012 HighestTide 2013 HighestTide 2014 HighestTide 2015
mAOD Date mAOD Date
Millport South West 2.14 2.15 2.19 2 Feb 2014 2.15 23 Jan 2015
Ullapool North West 2.95 2.98 3.10 1 Feb 2014 3.01 22 Jan 2015
Wick Far North East 2.14 2.16 2.25 11 Sep 2014 2.29 30 Sep 2015
Moray Firth Moray Firth 2.60 2.60 2.74 11 Sep 2014 2.78 30 Sep 2015
Aberdeen North East 2.46 2.43 2.58 11 Sep 2014 2.63 30 Sep 2015
Leith Firth of Forth 3.14 3.11 3.3 11 Sep 2014 3.34 30 Sep 2015

Areas of low-lying topography are most at risk of flooding. Outside Scotland in French Guiana, for example, the super tides will cause a 6 cm increase in the average spring tide height, which will lead to a 90 m shoreline retreat (http://www.nature.com/ngeo/journal/v1/n3/full/ngeo127.html). So the threat posed by super-tides depends strongly on the nature of the local coastal area.

Storm surges

Storm surges occur due to the winds and low pressure associated with a large depression or storm. Low atmospheric pressure allows the local sea surface to rise, and strong winds can pile up water against a coastline. Combined, these two effects can elevate sea level by several meters (the storm surge during Hurricane Katrina in the Bay of Mexico in 2005 was about 9 m). Closer to home, in January 2005 a large storm (see figure) created a storm surge which elevated the normal level of the tides in the north coast of Scotland by 1.5 meters. The storm led to significant flooding in communities along the north coast of Scotland.

Storm

12 January 2005 storm

 

Janet_Street

View over the river from Janet Street, Thurso, 12 Jan 2005

 

Scrabster

Scrabster Harbour office front door, 12 Jan 2005

 

Thurso

Thurso Harbour 12 Jan 2005

 

For more information, contact:

Dr Jason McIlvenny, Post-Doctoral Research Associate, Environmental Research Institute, North Highland College UHI. jason.mcilvenny@uhi.ac.uk

Dr Philip Gillibrand, Senior Research Fellow, Environmental Research Institute, North Highland College UHI. philip.gillibrand@uhi.ac.uk  Tel: 01847 889686

 

A Very Viking Christmas? Yule be surprised!

With merchandise from Disney’s Scandinavian-inspired animation Frozen expected to top toy gift lists this year and the increasing popularity of Scandinavian-style festive jumpers, staff from the University of the Highlands and Islands’ Centre for Nordic Studies give an insight into how Viking culture has influenced Christmas traditions.

Yule Festival

While Christmas is predominantly viewed as a Christian celebration, many of the traditions associated with it are thought to have origins in Viking culture. Scandinavian people marked the time around the winter solstice, when daylight hours start to lengthen, long before Christianity came to Nordic regions. They would prepare food, brew alcohol and visit friends and relatives in the festival known as Yule, a term possibly derived from the Old Norse “jól”.

Dr Alex Sanmark, reader at the Orkney-based Centre for Nordic Studies, explains: “The meaning of “jól” is uncertain and no satisfactory explanation has been put forward, but suggestions have ranged from “the time of blizzards” to “joyous feast” and even “magic”.

“Drinking played an important part in “jól” celebrations. According to early Christian laws, all the farmers had to join together to brew beer for Christmas and this beer should then be drunk at a party for “peace and prosperity”. This is clearly a Christian version of a much older, pagan tradition relating to the fertility cult – a form of nature worship used to try to ensure that people, plants and animals were productive. One of the earliest usages of the word “jól” is in a poem probably composed around 900, where we find the typical expression “to drink jól”, again showing that alcohol was a central part of Viking midwinter celebrations.”

Singing, acting and Santa? 

A further Nordic tradition associated with Christmas involves dressing up, visiting houses and singing songs. Dr Ragnhild Ljosland, a researcher at the University’s Centre for Nordic Studies, reveals:

“Another custom surrounding Yule is that of dressing up in costumes and engaging in community drama. As a child in Norway in the 1980s, I remember dressing up to “gå julebukk” – to go Yule-goating. Julebukk involves dressing up with a mask and going to people’s doors to chase out Christmas around New Year time. You sing and carry a sack to collect cakes and sweeties.

“If we go a couple of hundred years further back in time, people used to walk in a group around the farms in the parish, dressed up so that nobody would recognise them. It was the custom for them to be offered something to drink and eat at each farm. These costumes could be rather frightening and represent fantastical animals, such as an effigy of a billygoat’s – or Yule Goat’s – head on a stick. Folk belief had it that supernatural beings were extra active at this time of year, so the costumes could also have represented the “Oskoreia” – a frightening collection of supernatural creatures chasing about. It was best to stay indoors when the Oskoreia sweeps across your farmyard.”

Another creature in Scandinavian folk belief was a small being known as the “tomte” or “nisse”, thought to live in byres and stables.

Dr Ljosland notes: “The “tomte” or “nisse” was an elf-like creature in grey clothing and a pointed hat. It was a good idea to be nice to this being, for example by offering him some food and drink now and then, as he could be helpful if you were kind to him and naughty if you were not. Nowadays, the “Jultomte” or “Julenisse” (“Yule-tomte” or “Yule-nisse”) is the one who brings presents on Christmas Eve. As a child living in a city, I remember putting out Christmas porridge for the “nisse” in our garage, in the lack of a stable. But it must have worked as it was all gone on Christmas morning!”

Aspects of these customs are echoed in aspects of the festive season we know today, including carol signing, Santa Claus and his elves, pantomime and first-footing.

Frozen

A more recent addition to many families’ experience of Christmas is the Disney blockbuster, Frozen. Loosely based on the fairy tale The Snow Queen by Danish author Hans Christian Andersen, the film is full of references to Scandinavia and its traditions. The animation is set in Arendelle, a mythical kingdom inspired by the fjords, mountains and architecture of Norway. It features several items associated with Scandinavian history and culture, including Nordic runes, a maypole and trolls.

Professor Donna Heddle, director of the Centre for Nordic Studies, summarises the relationship between Nordic culture and Christmas: “There is no doubt the North has had an influence on the modern concept of Christmas and this is now being seen in popular culture, for example, in films like Disney’s Frozen.

“There is a real place in Norway called Arendal and Orkney gets our municipal Christmas tree from there every year – an interesting link which bridges the real and the imagined Nordic world.”

The Centre for Nordic Studies is part of Orkney College UHI, one of the University of the Highlands and Islands thirteen partners. You can find out more about its work and courses at www.uhi.ac.uk. The next intake for its Viking Studies course is January 2015.