Mid-Holocene and Anthropocene Climate Changes Affect the Carbonate Coast of Bar Al Hikman: Arabian Sea, Oman

Climate change, anthropogenic stressors, and rapid sea-level rise threaten coastal areas globally. In the tropics, coral reefs play a vital role, safeguarding the coasts from direct impact of waves and storms. This study presents the evolution of carbonate coast of Bar Al Hikman, a remote and pristine area along the Arabian Sea coast of Oman that hosts uncommon and monospecific coral reefs under monsoonal conditions. We employ sedimentological studies to offer a geological view spanning about 6000 years and use quantitative satellite image analysis to document the coastal shifts of the past half-century. These coral reefs have been producing carbonate sediment to shape the shoreline for at least 5000 years. However, they have experienced a drastic decline over the past 50 years and their extent has been reduced by 12% per decade. One direct consequence is the rapid retreat of the shoreline behind the disappearing reefs. Approximately 47% of the shoreline is retreating at a rate of over 1 meter per year, while 12% retreat at rates exceeding 5 meters per year. If the current pace continues, the coral reefs are predicted to disappear before the end of the century. This could accelerate shoreline erosion, the landward retreat of coastal barriers, and consequently the closure of the lagoons sheltered by reefs and barriers that host rich coastal ecosystems. Furthermore, with the ongoing global sea-level rise a significant portion of the 550 km2 of the Peninsula will fall below the annual flood limit, expediting the extension of sabkhas.