Tracking Nile Delta Vulnerability to Holocene Change

Abstract

Understanding deltaic resilience in the face of Holocene climate change and human impacts is an important challenge for the earth sciences in characterizing the full range of present and future wetland responses to global warming. Here, we report an 8000-year mass balance record from the Nile Delta to reconstruct when and how this sedimentary basin has responded to past hydrological shifts. In a global Holocene context, the long-term decrease in Nile Delta accretion rates is consistent with insolation-driven changes in the ‘monsoon pacemaker’, attested throughout the mid-latitude tropics. Following the early to mid-Holocene growth of the Nile’s deltaic plain, sediment losses and pronounced erosion are first recorded after ~4000 years ago, the corollaries of falling sediment supply and an intensification of anthropogenic impacts from the Pharaonic period onwards. Against the backcloth of the Saharan ‘depeopling’, reduced river flow underpinned by a weakening of monsoonal precipitation appears to have been particularly conducive to the expansion of human activities on the delta by exposing productive floodplain lands for occupation and irrigation agriculture. The reconstruction suggests that the Nile Delta has a particularly long history of vulnerability to extreme events (e.g. floods and storms) and sea-level rise, although the present sediment-starved system does not have a direct Holocene analogue. This study highlights the importance of the world’s deltas as sensitive archives to investigate Holocene geosystem responses to climate change, risks and hazards, and societal interaction.

The 4.2 ka BP event in the Levant

“…The source of the Blue Nile, Lake Tana (Fig. 3), also manifests a drier phase, leading to a reduction in Nile flow during the same period (Marshall et al, 2011), in phase with other regional paleoclimate archives (Chalié and Gasse, 2002;Thompson et al, 2002). This drop in and/or failure of Nile floods was recorded by a decreased Nile sediment supply ( Fig.…”

Assessing Land Deformation and Sea Encroachment in the Nile Delta: A Radar Interferometric and Inundation Modeling Approach

“…We anticipate significant variations in deformation rates throughout the investigated period, if the deformation is caused by anthropogenic factors, and negligible variations if caused by natural drivers. The latter, but not the former variations, occur at much longer time spans (thousands to tens of thousands of years; Marriner et al, 2013). Several recent developments, including the new gas discoveries in the Nile Delta (Ghassal et al, 2016) as well as the progressive increase in groundwater extraction over the past three to four decades (Mabrouk et al, 2013) within the delta and in its surroundings, suggest that the anthropogenic-related deformation is likely to intensify with time, so will the inundation in northern delta.…”

Egypt's Nile Delta in Late 4000 Years BP: Altered Flood Levels and Sedimentation, with Archaeological Implications

“…A similar change was noted ca. 4000 years BP when Sr isotope ratios were examined in a separate core study on the western delta margin (Marriner et al, 2013).…”

“…This period correlates well with the ca. 4200 years BP event in lower Egypt explored by the MEDIBA team and other groups; this is associated with effects of regionally marked climate change episodes that affected Nile flows at that time (Hamdan et al, 2018;Kaniewski et al, 2018;Krom et al, 2002;Marriner et al, 2012Marriner et al, , 2013Stanley et al, 2003). These included primarily increased aridity, evaporation, salinization, and altered monsoonal rain patterns inducing lower Nile flows (Figure 2.12 of Said, 1993) that altered sediment transport and composition patterns identified in the lower Nile basin.…”