Those who have been walking around our coastal areas have recently have noticed the very low sea level. But what is the reason for this?
This is a phenomenon that began to be perceived at the end of February this year and continues to this day. In the original photo of the article you can see a view of the beach area in Tsilivi on 25/2/2021. The low sea level both on our shores and on the shores of most of the Mediterranean has triggered a number of scenarios. The explanation is much simpler however.
From 19/2/2021 onwards, in particular essentially from the end of the extreme weather conditions “Medea” and onwards, our country, like most of the Mediterranean, is under the influence of very high atmospheric pressure, which for a period longer than 15 days exceeded 1020 or even 1030mb (milibars). This practically means that the atmospheric air exerts more pressure on the surface of the earth (hence the sea). An average value of atmospheric pressure is roughly considered to be close to 1013-1015mb. The diagram from the Northmeteo meteorological station in the area of Lefkos Pyrgos in Thessaloniki is typical. From 10/2/2021 onwards the atmospheric pressure began to increase, but after the end of the bad weather “Medea” most of the Mediterranean was covered by an extensive anticyclone, ie a field of increased atmospheric pressure, which is also associated with light winds and winds of summer.
The phenomenon, however, is not local. On the contrary, the following meteorological map depicting the situation on 25/2/2021 shows the entire extent of the anticyclone (with atmospheric pressure> 1030 in much of the Mediterranean – white equilateral curves).
It is noted, however, that in our wider area it is not uncommon to establish a field of high atmospheric pressure during the year. False news is circulating on many sites that the recent drop in water levels has astronomical causes and is essentially the effect of the tide caused by the planets. This tide usually has invisible effects in the Mediterranean, while on the contrary its effects are visible and easily perceived on open ocean shores (eg western Europe, where the difference in level within a day can be up to 1 meter) . It is also noted that the low tide caused by the gravitational pull of the planets, does not show such a prolonged duration, while it is usually of the order of a few centimetres. Although the gravitational pull of the moon and sun on the earth could amplify the phenomenon of lower sea levels in the Mediterranean, the main reason for this is the increased atmospheric pressure. The tide in the Mediterranean is usually perceived in narrow sea areas (such as in Chalkida). According to a scientific paper published in the international journal AGU, sea level can drop by 1 cm for every 1mb increase in atmospheric pressure. Similar images had appeared on 8/12/2015 off the coast of Greece, with a typical example in Nafplio. Again, of course, the drop in the level was caused by a prolonged period of high pressures in our area as shown in the following meteorological map (see the white equal curves above our area, which indicate an atmospheric pressure above 1030-1035Mb).
Research teams are looking into the phenomena as the picture shows below it seems that areas with the red arrows down are those where tides are low. The areas with arrows horizontal are areas that show a steady fall or no change at all.
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