“…We could not deploy traps or instruments in the winter due to water freezing in sediment traps and around sensors. Thus, winter sedimentation was not assessed, and our study excludes sediment delivered to the marsh via ice rafting (Argow et al., 2011; Fitzgerald et al., 2020b).…”
Section: Methodsmentioning
confidence: 99%
“…Most recently, Fitzgerald et al. (2020a, 2020b) found that sediment‐laden ice rafted onto the marsh surface during the winter storm season was a significant source to Great Marsh in Barnstable, MA (for example, a January 2018 Nor'easter delivered the equivalent of 15 years of clastic sediment).…”
Tidal salt marshes are critical protectors of the coast; they buffer against erosion and flooding (Möller et al., 2014), sequester carbon (Chmura et al., 2003), provide habitat to juvenile species and migratory birds (Boesch & Turner, 1984;Hughes, 2004), and filter pollutants and excess nutrients (Sousa et al., 2010). Coastal wetland maintenance involves complex biophysical feedbacks between clastic (i.e., inorganic) sediment supply, nutrients, plant growth, and flooding (Deegan et al., 2012;Kirwan & Megonigal, 2013). Deposition of clastic sediment in the form of clays, silts, and sands allows marshes to accrete faster than would be possible via in-situ organic production alone; thus, the availability and delivery of clastic sediment is a key factor in determining salt marsh resilience to erosion and future sea level rise (e.g.,
“…We could not deploy traps or instruments in the winter due to water freezing in sediment traps and around sensors. Thus, winter sedimentation was not assessed, and our study excludes sediment delivered to the marsh via ice rafting (Argow et al., 2011; Fitzgerald et al., 2020b).…”
Section: Methodsmentioning
confidence: 99%
“…Most recently, Fitzgerald et al. (2020a, 2020b) found that sediment‐laden ice rafted onto the marsh surface during the winter storm season was a significant source to Great Marsh in Barnstable, MA (for example, a January 2018 Nor'easter delivered the equivalent of 15 years of clastic sediment).…”
Tidal salt marshes are critical protectors of the coast; they buffer against erosion and flooding (Möller et al., 2014), sequester carbon (Chmura et al., 2003), provide habitat to juvenile species and migratory birds (Boesch & Turner, 1984;Hughes, 2004), and filter pollutants and excess nutrients (Sousa et al., 2010). Coastal wetland maintenance involves complex biophysical feedbacks between clastic (i.e., inorganic) sediment supply, nutrients, plant growth, and flooding (Deegan et al., 2012;Kirwan & Megonigal, 2013). Deposition of clastic sediment in the form of clays, silts, and sands allows marshes to accrete faster than would be possible via in-situ organic production alone; thus, the availability and delivery of clastic sediment is a key factor in determining salt marsh resilience to erosion and future sea level rise (e.g.,
“…Further research is needed to evaluate the eventual disposition of the coarse sediment fraction entering through the inlet. For example, an observation that peat in Plum Island Sound marsh is composed chiefly of silt and fine sand 74 suggests that imported coarse sediment could contribute to marsh mineral accretion. Likewise, incorporating the effects of vegetation, and waves and major storms would aid in making the modeling predictions more robust.…”
Much of the world’s population lives close to coastlines and this proximity is becoming increasingly impactful because of sea-level rise (SLR). Barrier islands and backbarrier saltmarshes, which comprise >10% of these coasts, are particularly susceptible. To better understand this risk, we model backbarrier morphologic and hydrodynamic evolution over a 200-year period of SLR, incorporating an erodible bed and a range of grain sizes. Here, we show that reduction in intertidal area creates negative feedback, shifting transport of coarse sediment (silt and sand) through the inlet from net export to net import. Imposing a modest marsh vertical accretion rate decreases the period of silt and sand import to 40 years (years 90 to 130) before being exported again. Clay is continuously exported thereby decreasing inorganic deposition on marshes and threatening their sustainability. Simulated marsh loss increases tidal prism and the volume of sand contained in ebb deltas, depleting coastal sand resources.
“…This back-barrier marsh has a tidal range of 2.6 to 2.8 m and consists of marsh and large open water areas with sandy shoals. The estuaries in the system provide low suspended sediment input 35 , and the mean grain size across the marsh is approximately 24% sand, 58% silt, and 17% clay 36 . Figure 5 Map of Great Marsh study site.…”
Salt marshes are threatened by rising sea levels and human activities, and a major mechanism of marsh loss is edge retreat or erosion. To understand and predict loss in these valuable ecosystems, studies have related erosion to marsh hydrodynamics and wave characteristics such as wave power. Across global studies, erosion is reported to be largely linearly related to wave power, with this relationship having implications for the resilience of marshes to extreme events such as storms. However, there is significant variability in this relationship across marshes because of marsh heterogeneity and the uniqueness of each physical setting. Here, we investigate the results of individual studies throughout the world that report a linear relationship and add a new dataset from the Great Marsh in Massachusetts (USA). We find that most marsh wave power and erosion data are not normally distributed and when these datasets are properly plotted to account for their distributions, the resulting relationships vary from previously published curves. Our Great Marsh data suggest that events from specific wind directions can have an outsized impact on edge erosion due to their larger fetch and wind speeds. We also find that factors other than wave attack such as edge erosion along tidal channels, can have a measurable impact on retreat rates. We show the importance of maintaining statistical assumptions when performing regressions, as well as emphasize the site-specificity of these relationships. Without calibration of a marsh erosion-wave power relationship using robust regressions for each individual marsh, such a relationship is not fully constrained, resulting in unreliable predictions of future marsh resilience and response to climate change.
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