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Ancient Sea-Level Rise Linked to Settlement Decline

Israeli scientists are studying the past to understand the potential future devastation of rising sea levels.

(CN) --- Israeli scientists are studying the past to understand the potential future devastation of rising sea levels.

Recent archaeological observations and multidisciplinary research from Dor, a settlement along the Carmel coast in northern Israel, shed new light on how fluctuations in relative sea level (RSL) influenced the history of this ancient dwelling that’s mentioned in the Bible.

The earliest remains at the site date back to the Canaanite period ending about 1200 B.C. After the Phoenicians settled at Dor around approximately 1100 B.C., the place became King Solomon’s main port on the Mediterranean. Today the settlement has a population of 440.

Now scientists are translating archeological indicators into historical sea-level information using high-resolution elevation measurements and dating. Some of these recently discovered sea-level markers date back to the early Holocene and include submerged prehistoric settlement constructions. Other markers, including fishponds, harbor structures, quays and coastal wells from later periods, proved useful in assessing sea-level fluctuations over thousands of years.

Israel’s Carmel coast is ideal for reconstructing relative sea level from the Middle Bronze to the Roman period due to the micro-tidal nature of the Israeli coast, its relative tectonic stability, and the fact that the coast and parts of the submerged zone have been occupied by humans almost continuously during the Holocene.

“This left a rich record of submerged and coastal settlements from the 8th-2nd millennium BCE, which had first negotiated the challenges of climate changes, rising sea levels, but then were severely impacted by the turmoil of the Bronze Age World System collapse,” according to a new study published in the journal PLOS One.

Coastal habitation recovered during the Iron Age, circa 1200–530 B.C. The area’s inclusion into the Hellenistic cultural sphere and later the Roman Empire further strengthened the coastal sites, with artificial harbor construction increasing during this time.

Researchers used a heavy-lift octocopter drone to collect photogrammetric data to create a digital surface model of the coastal tide of Dor. Survey data was georeferenced with GPS to produce nine new RSL data points to the 13 existing points, “significantly improving the resolution of sea-level change in the Southern Levant between the Middle Bronze Age and the Roman period,” according to the study. The dataset includes upper and lower limits of man-made structures that originally were built above sea level, as well as coastal pools, wells and concentrations of cargo or anchors.

Abrupt relative sea level rise in the course of a few hundred years between the Hellenistic and Roman periods raises questions on both the influence of this rise on coastal structures, mainly harbors, and also horizontal coastline changes.

The rapid rise of sea level would have directly impacted marine installations and the economy, which closely relied on them.

“Settlements which employed built coastal features would have been vulnerable as far as their maritime related endeavors were concerned, since the installations on which they relied would have gone out of use at a rapid pace, even if they attempted to repair and adjust them to the rising sea level,” the study states.

This means the sea walls built to protect the harboring ships, along with the quays to facilitate the loading and unloading of cargo, would have been rendered dysfunctional.

Dor’s coastal fortification would have also been diminished by rapid sea-level rise and may explain the lack of fortifications in Dor during the Roman period.

The corresponding infrastructure degradation would have affected the harbor city’s economy.

“To be sure, political implications would have followed, and the coastal cities of the Southern Levant may well have found themselves in a weakened position when they had to face the expansionist ambitions of the Hasmonean dynasty, and later the encroachment of the Roman Empire," the study states.

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