Lagoon-barrier system response to recent climate conditions and sea level rise, Mozambique, Africa

Abstract

Transitioning lagoon-barrier systems and coastal transgressive dunes offer the valuable opportunity to correlate their formation and interactions with seasonal dry and wet climate conditions, stepped relative sea-level rise of ∼3.5 m, and sediment supply at various scales. This manuscript examines the Holocene sea level changes and recent climate conditions and controls on a 150 m-high coastal barrier system in Mozambique, southeastern Africa. The methodological approach was based on the use of 7 kyr B.P. relative sea-level curve; 37 years of wind records from 1979 to 2016; 52 years of rainfall records from 1960 to 2012; and 56 years of average recorded temperatures from 1960 to 2016. Local dunefield migrations were monitored and the sand transport rate was measured from 2016 to 2017. The combined effects of the relative sea-level rise and sediment supply indicate the formation of the lagoon-barrier system in southern Mozambique. While the recent dry and wet climate conditions suggest that they might be a controlling factor on the generation of transgressive dunefields that migrate landward. This migration is reflected on the sand transport rate of 1.4 kg m−1 s−1, which is controlled by winds from the SSW, the S and the SSE quadrants. The active parabolic dunes monitored, indicated a SE-NW migration rate of 22.5 m yr−1, which rapidly buries lakes and lagoons systems. The formation of different geomorphological features on the transgressive paleodunes and modern dunes reflect their exposure to prevailing S, SSE, SE, E and N winds, the annual rainfall of 1600 mm yr−1, and the absence of rain for 7 months yr−1. The stepped Holocene sea-level changes combined with high sediment supply and persistent acting of seasonal dry and wet climatic conditions led on the sedimentation and definition of transgressive dunefields morphology in southern Mozambique coast.