ABSTRACT

THE GIANT UNDERWATER WATERFALL AT ICELAND (December 2023): The Denmark Strait is the largest underwater waterfall in the world: both in terms of height and flow. The water masses with different temperatures and salinities are separated. Cold salt water is denser than warm water, and warmer water is stratified on top. The cold salt water then flows like a veritable underwater river, obeying gravity and plunging down to the depths when it hits a precipice. Underwater waterfalls are plentiful, so much so that the largest waterfall on earth is underwater between Greenland and Iceland, in the Denmark Strait. The water flowing from the northern Greenland Sea towards the Irminger Sea at the southern end of the Denmark Strait is relatively cold. Immediately before entering the warmer Irminger Sea, the water falls from a 3505-metre-high cliff at a rate of 5 million m³ per second. Fortunately, the 3.5-kilometre-high Denmark Strait waterfall is almost safe from the harms of human activity, although climate change is warming the Arctic seas, with plenty of fresh, almost salt-free meltwater diluting the Arctic Ocean. When warm salt water freezes, it freezes out the salt, turning it into thick cold brine. This process feeds the currents. From submarines, many eddies, large and small, have been observed where the cold salt water sinks. Over time, less cold salt water from the Greenland Sea will flow through the Denmark Strait. At that point, the important current for Europe - the NOAA North Atlantic Current, of which the Gulf Stream is only a part - will slow down and possibly stop in the distant future. The centre of gravity of the area where the eddies descend will shift north in summer and south in winter, depending on the seasons. The location of the centre of gravity and the salinity also influence the strength and intensity of the current. The intensity of the current (yield, which has a dimension of  m³/month) is difficult to measure and estimate. The dependence of the intensity on the velocity of the flow is linear. The dependence of flow velocity on temperature is not known precisely, but its linear dependence on temperature can be measured with markers (tracking balls). Suggested measurement of the sream speed: in the warm branch of the current, a large number (a few hundred) of GPS tracking balls (passive device: could be a microwave corner reflector but the reflectors need flying locator) that will disperse (and possibly sink) in the cold water, and repeat the measurement in winter..Less polar ice is expected each summer. Temperate energy consumption for cooling is expected to increase in the coming years: the European half of the summer ice will shrink onto the high mountains of Greenland..

A tengervíz kifagyása, sűrűsége (kg/m³) a sótartalom és hőmérséklet függvényében (https://aquarius.oceansciences.org/activities/density_SWmix_sink.pdf)

Az áramlatok Grönland környékén, a kékkel jelölték a hideg áramlatokat

(https://education.nationalgeographic.org/resource/global-conveyor-belt/)

Az évente kifagyó jég mennyisége 1000 km³ -ben és havi bontásban. Az áprilisi-májusi maximumok az utolsó néhány évben keveset változnak (a téli sötétség miatt), a kemény poláris fagyok megmaradnakak. Ez jó hír! (https://www.arcticdeathspiral.org/)

A nyári megfagyott jég mennyiségét jellemző fekete színű szeptemberi görbe lefutása nem jó hír: évről-évre kevesebb sarki jég várható nyáron. A mérsékelt égővön a hűtésre használt energiafogyasztás növekedésére számíthatunk az elkövetkező években (előrejelzés: fekete szaggatott vonal az ábra közepén, https://www.arcticdeathspiral.org/). A nyári jégtakaró európai fele rá fog zsugorodni a grönlandi magas hegyekre.