Deltaic response to climate change: The Holocene history of the Nueces Delta

Abstract

Deltas host large urban centers and expanses of coastal wetlands worldwide. As such, their future will play an important role in the economic and ecological health of many coastal communities. Although threats to deltas from drowning due to subsidence and accelerating sea-level rise are well-studied, far less is known about the physical effects of climate change on deltas. Here we map the location of the Nueces Delta shoreline of the northwestern Gulf of Mexico over the last ~8.0 ky to show that the delta retreated and prograded at rates greater than 10 m/yr and over distances of up to 22 km in a few centuries at the same time as independent proxy records of Holocene climate change indicate decreased and increased effective precipitation, respectively. These periods of retreat occurred at 5.0 and 3.2 ka; an earlier, previously documented period of retreat at 8.2 ka was driven by a rapid increase in the rate of sea-level rise. The Nueces Delta experienced periods of progradation at 6.6 ka, 3.8 ka and 2.2 ka. As some of these changes may have been driven simply by avulsion or other autogenic processes, we test the role of climate in driving these changes by quantifying the amount of sand, thought to be a conservative proxy for sediment flux, within the delta through the Holocene. The amount of sand delivered to the delta increased during periods of progradation and decreased during periods of retreat. These changes occurred despite decreasing rates of sea-level rise through the middle Holocene. These results suggest that deltas are susceptible to not only increasing rates of sea-level rise, but also other climatic-related forcings, such as those that modulate sediment supply. These stresses will be amplified in the future by decreased sediment supply to deltas due to the damming of their rivers. • We reconstruct the Holocene history of the Nueces Delta. • The delta retreated in response to dryer climates at 5.0, and 3.2 ka. • The delta prograded in response to wetter climates at 6.6, 3.8, and 2.2 ka. • Deltas are susceptible to rapid retreat caused by climate changes.