 And our next speaker is Julia Moriati, Julia's professor at the University of Colorado Boulder as well. And she's going to talk about variability in Marsh estuary sediment exchanges in back barrier systems, Bargain and Bay in New Jersey, sorry if I, yes we can go ahead. Bargain Bay and so thanks Albert and to the CSDMS IF team for organizing this series. Today I'll be talking about some work I started at the USGS as a postdoctoral fellow with Neil Gangew. Julia. Oh yeah. All right we're seeing your presenter view. Can you flip the screen to show the slide? Yeah, how, do you know how to do that? Try, do you have two screens? Yeah. You have to share, try sharing PowerPoint directly versus the screen. Okay. If you start the presentation and then switch to zoom and then share screen you can point to the slide. So share PowerPoint. Yeah, start the slides. There you go, there you go. Okay, great. You're up. Okay. Okay, so this work was done with colleagues at USGS and specifically today I'll be talking about part of the work focusing on spatial variability in marsh estrange sediment fluxes in Bargain Bay, New Jersey which is a back barrier estuary. So in terms of the sediment exchanges specifically I'll be talking about marsh edge erosion which is the process by which waves and other incurrents erode the sediment from the edge of the marsh and then also deposition on the marsh platform or the marsh surface. And we're interested in these sediment exchanges because they affect marsh changes in marsh geomorphology which then affect the ability of marshes to provide ecosystem services including habitat, carbon burial, as well as protection from storms. So today we used a numerical modeling approach and we implemented the coast model which is a coupled ocean atmosphere wave sediment transport model for Bargain Bay, New Jersey. This coast model includes the hydrodynamic model runs as well as the swan wave model and the CSTMS sediment transport model. So this is a very similar modeling setup to what Kevin was describing a few talks ago. We implemented the model for Bargain Bay, New Jersey which as I mentioned is a back barrier system you can see an aerial image of it on the top right and then on the left hand side you can see the symmetry of the system that we put into the model. So as an introduction to Bargain Bay it is bordered on its oceanward side by two long barrier islands and characterized by two inlets. So in the south you have little egg inlet down here and then in the center you have Bargain Inlet on the right hand side. These green areas are marshes and so you can see there's large marshes in the southern portion of the bay and then you get these smaller patchier marshes in the northern portion of Bargain Bay. And the symmetry is pretty shallow it's only a couple meters deep and the location of these channels is going to come back throughout the talk. So the location of the inlets is going to be important. Okay so we implemented as I mentioned the coast model and we chose this model and it had previously been implemented to look at sediment transport during Hurricane Sandy but for this study we also took advantage of some of the recent coast upgrades or new processes that have been incorporated into coast including the vegetation hydrodynamic feedbacks based on Bowdoin at all and as well as the marsh edge erosion which allows sediment to be eroded from the edge of marsh grid cells and put into the estuary where it can then be transported and redistributed within the estuarine marsh system. And this we assumed that this edge erosion at the edge of the marsh was proportional to wave thrust so areas with higher more energetic waves and higher water levels to a point will erode more material from the edge of the marsh. Okay so then we took this model as I mentioned we implemented it for Bargain Bay and so the first one the first things we looked at was time averaged maps of the hydrodynamic conditions as well as marsh edge erosion. So here on the left hand side you're looking at time average bed shear stress with the darker colors for all these maps the darker colors indicate higher values or faster rates. And then for the middle panel you're looking at depth integrated suspended sediment concentration and then on the right you're looking at both wave thrust and marsh edge erosion. Remember these are proportional to each other so they can be shown on the same plot. One thing I want you to notice is that for the hydrodynamic conditions as well as the edge erosion these you had the higher values near the inlets of the system this is because you're getting fast tidal currents and propagating in and out you're getting waves propagating into the estuary and that's driving these higher this more energetic hydrodynamics that are then causing these higher values of wave thrust near the inlets. This is especially true in the little egg inlet although in a little bit less true here although because the energetic hydrodynamics are more limited and don't affect this shore across from it as much. So then after looking at the spatial variability in marsh edge erosion we started looking at how sediment that's eroded as well as sediment that's resuspended from the estuary itself is making its way back onto the marsh or the degree to which it is and so for one of in order to look at this I'm going to show you a scatter plot of modeled deposition on the marsh platform on the y-axis on a log plot and then on the x-axis we you're looking at distance to a high thrust region so remember that's really going to be these areas near the inlets as well as this area that's downstream of this estuarine channel right here and so when you're looking at this the areas near high thrust those are the areas near high thrust regions and you can see as you get closer to these high thrust regions so as you get closer to the zero distance of zero you're getting more deposition on the marsh platform. A secondary effect was this distance to estuarine channel but part of this effect was also incorporated into the distance to high thrust region and so in conclusion we've implemented a hydrodynamic wave sediment transport model which accounted for marsh edge erosion as well as the presence of vegetation for this back bear estuary in New Jersey for a four month period in 2012 and we saw that for both erosion from the edge of the marsh as well as deposition back on top of the marsh but these rates were higher near areas of energetic waves or high wave thrust which is to say primarily near inlets and with that I will end it I think I'm right at seven minutes and thank you. Thank you so much Julia so Julia I gave the last talk here are there any questions for Julia? I realized we're a little bit over time but I think one or two questions should be possible if not I'm gonna I'm gonna ask you one one question Julia so a little bit inspired by Jaap Nienhaus talk about sea level change do you if you or could your model you know accommodate sea level rise if you look at longer time periods and then still take into account vegetation if you've done some long-term runs or yeah so this is a pretty slow model right so for right now we're limited in terms of it's we've only really done model runs on the time scales of months so but in terms of I think you're getting at see how would sea level rise affect the results yes yes thank you is so one of the main rate ways that would affect the results is that wave thrust it increases as the water level reaches the edge of the marsh and so but then once the water level exceeds the height of the marsh and more of the energy from the wave starts propagating over the marsh edge into the marsh itself you start actually getting lower values of wave thrust and so lower erosion rates and then of course as the sea level rises the marshes flood more that can trap more sediment because there's more accommodation space on top of the marsh as well so it sort of would accelerate like they accelerate these processes the sediment you know yeah yeah no thank you let's see if there is another question if not then then this oh I see one question of Pani Juan can you you can unmute yourself and ask the question oh thank you I wasn't sure how to do this hi Julia this is just a curiosity out of curiosity how do you define the wave thrust yeah so wave thrust is the depth integrated dynamic pressure at the vertical edge of the marsh scarp and so how we found it is we took estimates of wave properties from the so we took estimates from the swan wave model as well as water levels from the roms hydrodynamic model to estimate wave thrust and then going a little bit beyond that because the marsh edge is sort of at the edge of the grid cells and not in the center we did some interpolation to get the wave thrust at the marsh edge itself well thank you thank you very interesting thank you for your question Pani and thank you Julia for for your presentation thank all speakers for your presentation