Sciency Thoughts: St John's County

Monday, 23 November 2020

Hurricane Eta exposes nineteenth century shipwreck on the coast of Florida.

Hurricane Eta swept across central Florida on 12 November 2020, causing eleven fatalities, in addition to the 178 it had already claimed in Central America, in addition to causing widespread flooding and causing about a billion dollars' worth of damage to property. After the storm had passed it was discovered that high tides brought on by the hurricane's storm surge had scoured the beach at the Fort Matanzas National Monument in St John's County on the east coast of Florida, exposing the remains of a ship that had been burried by the sand.

Exposed timbers on the foreshore at Fort Matanzas National Monument, believed to have come from an nineteenth century shipwreck. CNN.

The site is now being investigated archaeologists from the St. Augustine Lighthouse Archaeological Maritime Program and students from Flagler College, who have determined that the remains probably belong to the Caroline Eddy, an American merchant ship which sank in the area on 29 August 1880, after becoming caught in a storm.

Chuck Meide of the St. Augustine Lighthouse Archaeological Maritime Program examaning timbers believed to have come from the Caroline Eddy, a merchant ship which sank off the coast of Florida in August 1880. St Augustine.

Tropical storms, known as hurricanes in the Caribbean, are caused by solar energy heating the air above the oceans, which causes the air to rise leading to an inrush of air. If this happens over a large enough area the inrushing air will start to circulate, as the rotation of the Earth causes the winds closer to the equator to move eastwards compared to those further away (the Coriolis Effect). This leads to tropical storms rotating clockwise in the southern hemisphere and anticlockwise in the northern hemisphere. These storms tend to grow in strength as they move across the ocean and lose it as they pass over land (this is not completely true: many tropical storms peter out without reaching land due to wider atmospheric patterns), since the land tends to absorb solar energy while the sea reflects it.

The formation of a tropical cyclone. Natural Disaster Management.

Despite the obvious danger of winds of this speed, which can physically blow people, and other large objects, away as well as damaging buildings and uprooting trees, the real danger from these storms comes from the flooding they bring. Each drop millibar drop in air-pressure leads to an approximate 1 cm rise in sea level, with big tropical storms capable of causing a storm surge of several meters. This is always accompanied by heavy rainfall, since warm air over the ocean leads to evaporation of sea water, which is then carried with the storm. These combined often lead to catastrophic flooding in areas hit by tropical storms.

The formation and impact of a storm surge. eSchoolToday.

Warning issued to bathers after large numbers of Portuguese Man o' War wash up on Florida Beach.

The St. Augustine Beach Police Department, has issued a warning to bathers to be wary after large numbers of Portuguese Man o' War, Physalia physalis, have washed up on beaches in the city in St John's County, Florida, over the last two weeks. These venomous Cnidarians wash up on beaches in Florida at this time every winter, but this year they seem to be particularly numerous, possibly in response to the exceptionally severe storm-season in the Caribbean last year, which will have stirred up nutrients from the ocean floor, as well as washing them from the land, prompting blooms of the plankton upon which the Man o' War feed.

A Portuguese Man o' War washed up on a beach. Oceana.

Portuguese Man o' War are colonial Siphonophores only distantly related to true Jellyfish, Scyphozoa, though commonly referred to as such. Their bodies are made up of thousands of individual zooids, each with their own sting, tentacles and digestive system. New zooids are formed by budding from other members of the colony, but remain attached to these to form a single colony. Each year a generation of specialist sexual zooids (gonozoids) is produced which produce eggs and sperm, with fertilised eggs going on to form new colonies. These animals are anchored to the sea surface by a highly modified zooid which forms an air sack, filled with a mixture of carbon monoxide defused from the zooid and nitrogen, oxygen and argon from the atmosphere, which are brought into the sack through osmosis. Portuguese Man o' War produce an extremely strong venom, for both capturing food and defending the colony, and which is capable of causing extremely painful stings, and sometimes death, in Humans, for which reason people are advised to be extremely cautious on beaches where these animals wash up, not just of entire animals but also detached tentacles, which are less visible but still capable of stinging.