Field evidence for the initiation of isolated aeolian sand patches

TL;DR

This study provides field evidence for a new mechanism initiating isolated sand patches on non-erodible surfaces, involving changes in sand transport dynamics at surface boundaries, which explains early-stage dune formation in limited sand environments.

Contribution

It introduces a novel mechanism explaining sand patch initiation on non-erodible surfaces, supported by field observations of transport dynamics and patch formation.

Findings

Sand patches form due to changes in transport dynamics at surface boundaries.

Transport rate varies between erodible and non-erodible surfaces.

Field evidence supports the new initiation mechanism.

Abstract

Sand patches are one of the precursors to early-stage protodunes and occur widely in both desert and coastal aeolian environments. Here we show field evidence of a mechanism to explain the initiation of sand patches on non-erodible surfaces, such as desert gravels and moist beaches. Changes in sand transport dynamics, directly associated with the height of the saltation layer and variable transport law, observed at the boundary between non-erodible and erodible surfaces lead to sand deposition on the erodible surface. This explains how sand patches can form on surfaces with limited sand availability where linear stability of dune theory does not apply. This new mechanism is supported by field observations that evidence both the change in transport rate over different surfaces and in-situ patch formation that leads to modification of transport dynamics at the surface boundary.