Sciency Thoughts: Adriatic Sea

Showing posts with label Adriatic Sea. Show all posts

Wednesday, 9 March 2022

Fireball meteor over Italy.

Witnesses across much of northern and central Italy, as well as the Switzerland, Austria, southern Germany, and parts of Croatia, have reported observing a bright fireball at about 7.55 pm local time (about 6.55 pm GMT) on Saturday 5 March 2022. The fireball is described as having moved from northeast to southwest, first appearing over the Province of Arezzo in Tuscany and vanishing over the northern Adriatic. A fireball is defined as a meteor (shooting star) brighter than the planet Venus. These are typically caused by pieces of rock burning up in the atmosphere, but can be the result of man-made space-junk burning up on re-entry.

The 5 March 2022 Italian fireball seen from Croatia. Croatian Astronomical Union.

Objects of this size probably enter the Earth's atmosphere several times a year, though unless they do so over populated areas they are unlikely to be noticed. They are officially described as fireballs if they produce a light brighter than the planet Venus. The brightness of a meteor is caused by friction with the Earth's atmosphere, which is typically far greater than that caused by simple falling, due to the initial trajectory of the object. Such objects typically eventually explode in an airburst called by the friction, causing them to vanish as an luminous object. However, this is not the end of the story as such explosions result in the production of a number of smaller objects, which fall to the ground under the influence of gravity (which does not cause the luminescence associated with friction-induced heating).

Heat map showing areas where sightings of the meteor were reported (warmer colours indicate more sightings), and the apparent path of the object (blue arrow). American Meteor Society.

These 'dark objects' do not continue along the path of the original bolide, but neither do they fall directly to the ground, but rather follow a course determined by the atmospheric currents (winds) through which the objects pass. Scientists are able to calculate potential trajectories for hypothetical dark objects derived from meteors using data from weather monitoring services.

Friday, 15 November 2019

Venice suffers the worst flooding in 53 years.

The city of Venice in northern Italy suffered its second worst flooding since records began on Tuesday 12 November 2019, with waters reaching 1.87 m above average levels at high tide, a level surpassed only by the flooding of 1966, when the waters reached 1.92 m above average. The flooding is thought tohave caused hundreds of millions of euros of damage to the historic city, as well as causing two fatalities. Both of the known deaths associated with the flood occured on the island of Pellestrina, which forms part of the barrier between the Venetial Lagoon and the Adriatic Sea; one of the fatalities was reportedly due to a man beong electricuted while trying to start a pump in his flooded house, the cause of the other has yet to be disclosed.

Flooding in St Marks Square, Venice, on Tuesday 12 November 2019. /AFP/Getty Images.

The flooding was caused by a combination of a spring tide, in which the Sun and Moon are aligned either on the same side of the Earth or directly oposite (as was the case this week), leading to high tidal waters, and a storm surge caused by a low pressure system over the Mediterranean. The low pressure above areas of sea causes water to rise there by ~1 cm for every millibar drop in pressure, leading to a storm surge that can overwhelm low-lying coastal areas.

Animation showing how the alignment of the Sun and Moon causes higher 'spring' tides. NOAA.

Friday, 6 June 2014

A new species of Jellyfish from the North Adriatic Sea.

While instantly familiar and biologically simple, Jellyfish (Scyphozoa) are still in many ways poorly understood, with frequently poorly understood life-cycles and population structures, leading to unexpected shifts in population and sudden blooms of large numbers of Jellyfish, which can impact on commercial fisheries or have other unforeseen economic impacts.

In a paper published in the journal Zootaxa on 7 May 2014, a team of scientists led by Stefano Piraino of the Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali at the Università del Salento and the Consorzio Nazionale Interuniversitario per le Scienze del Mare, describe a new species of Jellyfish that unexpectedly produced a major bloom in the North Adriatic Sea from September 2013 till March 2014.

The new species is placed in the genus Pelagia, and given the specific name benovici, after the late Adam Benovic, an expert on the gelatinous plankton of the Adriatic. Pelagia benovici is a small Jellyfish, with a thin umbrella reaching 35-50 mm across at maturity. It is yellow ochre in colour, with a warty upper surface and oral arms. Both the oral arms and tentacles are white, as are the gonads.

Pelagia benovici in lateral view. Piraino et al. (2014).

Pelagia benovici appeared unexpectedly across a wide area of the Northern Adriatic in September 2013, forming dense blooms at depths of 20-25 m. While it is possible that the species is local, and has either suddenly changed its behaviour or has bloomed as part of a population cycle long enough to have not been observed previously, Piraino et al. deem this unlikely in an area as well studied as the North Adriatic, and instead speculate that it is recently introduced species. A number of introduced Jellyfish (and other) species have been recorded in the Mediterranean from the early twentieth century onwards, and the North Adriatic, particularly around the Gulf of Venice, is considered a hotspot for species introduction, due to the large number of ships passing through the area.

Map of sampling sites (stars) and observed distributional range (circles) of Pelagia benovici in the North Adriatic Sea. Piraino et al. (2014).