SUBMERGENCE OF THE HELLENISTIC HARBOR AT AKKO, ISRAEL: IMPLICATIONS FOR SEA-LEVEL RECONSTRUCTIONS IN THE LEVANTINE BASIN

With rising seas and impending inundation, a sound understanding of the factors controlling sea-level is imperative in order to accurately predict regional coastline changes. Such information can result from a variety of different sources, spanning from geological or biological markers of past sea-levels to archaeological indicators. This study utilizes a combination of such markers to better understand the causes for the submergence of the Hellenistic (3^rd to 1^st centuries BCE) harbor of Akko, located in the Eastern Mediterranean (northern Israel). Three possible reasons for the current sub-aerial position (1.1 to 1.2 meters below present sea-level) of these harbor remains were assessed: structural deterioration, eustatic sea-level rise, and vertical tectonic movements. The sloping surface of the harbor quay, as well as the harbor's construction on a cohesionless sediment fill indicate subsidence from structural deterioration. However, this deterioration only accounts for part of the elevational discrepancy. The remaining difference can be explained by comparison of the currently submerged harbor with other similarly dated submerged coastal structures in the Levant, which suggests a common sea-level rise of 1 to 2 meters. Together, these results show that an estimated ~1 meter of sea-level rise has occurred since the Hellenistic Period. Minor vertical displacements from tectonic activity cannot be ruled out and merit further investigation. This study emphasizes the complicated nature of sea-level, highlighting the importance of using proper construction methods for the coastal environment, as well as the inevitability of submergence with rising seas.