A rare astronomical event is currently taking place and we have witnessed its impact on North Sea tides during the last few days, peaking on Saturday. The event is of special interest to SpringTide – because we refer to its effects in the name of our company.
Every month, when there is a new moon or a full moon, “spring tides” are observed. These are higher tides than normal and are caused by the combined gravitational pull of the moon and sun becoming “yoked together” in alignment.
The term ‘spring tide’ actually has nothing to do with the season. It is derived from the Anglo-Saxon verb springan meaning ‘to spring, rise, swell, burst‘: and is used to describe the extra strength of the tides – more recently labelled “supertides” – that occur during these planetary alignments.
The new moon, which occurred last week, coincides with a point in the moon’s orbit in which it is closer to the earth than normal. This is also known as a ‘supermoon.’ When the moon is full, a supermoon can be 30% brighter than usual, as was observed several times last summer.
So, not only are the current spring tides occurring at the same time as a supermoon, they are also coinciding with a point in the lunar orbit when the moon is unusually close to the equator. In Astronomy, when the earth, sun and moon are aligned like this, it’s called a syzygy, which means ‘yoked together’.
This is a rare occurrence, multiplying the gravitational effects of the sun and the moon on the Earth. As a result, the joint highest spring tides for 18.6 years peaked over the weekend.