Field Campaign Plans for Late August 2019
Approximately 9 days of shiptime are planned for turning around oceanographic moorings, completing terrestrial surveys and servicing the met-station and for gathering further hydrographic information during the 2019 field season. The work will take place in late August from the R/V Ukpik. Work will be scheduled to avoid/work around any closures due to subsistence whaling.
The Captain of the R/V Ukpik is responsible for coordinating with local subsistence activities. All necessary permits have been secured to carry out this field workplan 2019.
2019 Sampling Goals
In order of priority, the goals of the 2019 field campaign are to:
- Retrieve, collect data, and redeploy the 3 year-round oceanographic moorings to measure currents, waves, near-bottom velocity and hydrography, sediment fluxes and water levels.
- Deploy shore-facing mooring
- Perform elevation/drone survey near met-station/service met-station.
- Geo-reference met-station camera images
- Quantify coastal elevations and shoreline position
- Resurvey strudel scour
- Survey entrance to Foggy Island Bay (FIB), resurvey one line from last year, and survey outside barrier islands.
- Deploy real-time wave buoy
- Measure water column hydrographic (currents, conductivity, temperature, suspended sediment size distributions, nutrients, total suspended solids, delO18) as well as seafloor information (elevation, backscatter and sediment grain size) within and outside of Foggy Island Bay
The information gathered during this field campaign will be used for verifying numerical simulations of wave hydrography within Foggy Island Bay. Bathymetric transects surveyed in prior years including a strudel scour surveyed in 2018 will be directly comparable to new bathymetry collected in 2019 for use in quantifying changes in bathymetry between surveys. At least one survey line from the 2018 field season will be resurveyed for direct comparison.
A total of 3 year-round and 1 seasonal mooring will be retrieved and redeployed in 2019.
Due to time constraints, the moorings will be retrieved and the same style moorings with the same or comparable instruments will be deployed in the same location. The majority of instruments will be replaced or will have the data downloaded on site and the batteries replaced before redeployment. By swapping out the moorings, the turnaround time and is reduced, thus leading to more time available to focus on other tasks.
The offshore mooring (Cross Island Mooring) measuring salinity, temperature, pressure, currents and waves is currently deployed offshore of the barrier islands to capture the offshore wave field. A real-time wave buoy measuring directional wave spectra will be deployed to the east of this offshore mooring in August when the offshore mooring is being retrieved and another mooring redeployed.
Within Foggy Island Bay two additional year-round oceanographic moorings (the UAF moorings and UAA mooring) will be retrieved and their replacement redeployed to continue measuring oceanographic conditions and sediment fluxes.
A seasonally deployed shallow water mooring (<3 m water depth) that includes an acoustic doppler velocimeter measuring pressure, temperature, water velocity at a point and acoustic backscatter and an optical backscatter sensor will be deployed at this time as well. This mooring will be deployed in August and will be recovered in September along with the real time wave buoy.
The coastal weather station from Campbell Scientific, deployed in Foggy Island Bay, provided real-time wind speed and direction, barometric pressure, temperature and relative humidity through December. It will be serviced and any necessary repairs made. The camera mounted on the met station will have their SD cards retrieved and all photos will be downloaded for analysis and geo-referencing. New SD cards will be installed to allow the cameras to continue capturing images.
Transects will be done along with an aerial survey using a UAV and RTK GNSS to provide coastal elevations and shoreline position for use in calculation of the volume of eroded coastline. UAV and GNSS surveys will take ~4 days.
~3 days of CTD/multibeam hydrography within and adjacent to Foggy Island Bay will be carried out from the R/V Ukpik using a combination of a Seabird Electronics SBE25 and/or an AML MinosX CTD system. The SBE25 is equipped with 6 4-L Niskin bottles and sensors to measure conductivity, temperature, depth, transmissivity, fluorescence and photosynthetically available radiation (PAR). Approximately 50 stations are planned for 2019, 45 AML and 12 water and CTD samples. The goal is to achieve station spacing of 5 km or less in order to adequately resolve the ~10 km Rossby Radius of deformation expected in the area.
A Laser In Situ Sediment Size and Transmissometer (a LISST 100X) will be mounted on the CTD rosette. The LISST 100X system measures the scattering angle of a laser to provide an estimate of the sediment size distribution through inversion.
An 600 kHz RDI Workhorse ADCP will be deployed from a davit mounted acoustic sled and towed alongside the vessel while it is underway. The ADCP will record water column velocity, surface temperature and acoustic backscatter. Together with the LISST data and calibrated OBS data from the CTD system, the ADCP data provides a means to quantify sediment fluxes over the course of the cruise. As far as we are aware, such data from this region will be unique.
A pole mounted Reson Seabat 7125 multibeam echosounder and an Applanix POS MV inertial measurement unit will be used to measure seafloor elevations and seafloor backscatter while underway. Water column sound velocity will be derived from the CTD measurements and applied to the multibeam soundings to correct for water column sound speed variations. Position data will be post-processed to provide sub-decimeter position accuracy in the horizontal and vertical directions.
Using a variety of sensors bathymetric elevations and seafloor backscatter, water column temperature, conductivity, optical backscatter, chlorophyll-a fluorescence, photosynthetically available radiation and scattering angles as well as water column velocity and acoustic backscatter will be measured again this field season. Salinity, sediment size distributions and sediment fluxes will be calculated from these measurements post-cruise.
Water samples will be collected using the CTD rosette at this time for lab analysis of TSS analysis. A ponar grab will be used to sample seafloor grain size. Water will be collected for nutrient analysis and delO18. Water column samples will be collected at a minimum of three depths (surface, bottom and mid-depth or at the subsurface chlorophyll maximum if one is evident) at the full stations shown in the 2019 field campaign map above.
2018 Field Campaign Wrap-Up
Persistent ice delayed the start of fieldwork in July 2018 by ~1 week and prevented most work outside of the barrier islands, except for a short foray outside the barrier islands to deploy a mooring, for the duration of the 10-day cruise between July 17 and July 26. While ice was a challenge, the weather was generally good throughout the 10-day cruise which allowed us to accomplish a great deal of survey work and to install multiple oceanographic moorings.
Between July 15th and July 30th, 2018 two bottom founded oceanographic moorings equipped with various sensors to measure currents, surface wave spectra, near-bottom velocity and hydrography and water levels were deployed in support of the Central Beaufort Sea Wave and Hydrodynamic Modeling Study project inside of Foggy Island Bay. A third, seasonally deployed shallow water oceanographic mooring, the “shore-face” mooring was deployed to measure shore face sediment fluxes at the southern end of Foggy Island Bay. A fourth mooring, the “LTER Cross Island mooring” equipped with sensors to measure currents, wave spectra and near bottom hydrography was deployed offshore of the barrier islands enclosing Foggy Island Bay for the Beaufort Lagoons LTER project. Data from this LTER mooring will be incorporated into results for the Central Beaufort Sea Wave and Hydrodynamic Modeling Study. Specifically, the LTER mooring will provide information on the “boundary conditions” for wave and hydrographic conditions within Foggy Island Bay.
Water column hydrographic information were collected (conductivity, temperature and pressure) during the cruise in order to provide sound speed corrections for multibeam sonar data and information on the origin and characteristics of the water masses in the study area. A total of 14 CTD+discrete water samples stations (using a Seabird Electronics SBE25/55 CTD +Water Sampler) and 50 sensor only stations (using an AML Oceanographic CTD+Turbidity probe) were completed during the cruise.
The complex hydrography of the region (multiple small-scale frontal features between riverine, ambient shelf water and sea ice melt derived waters) means that high resolution hydrographic information is required to ensure the accuracy of the multibeam sonar mapping efforts.
Multibeam sonar data (seafloor depth and backscatter strength) gathered within and outside of Foggy Island Bay will be used for creating a Digital Elevation Model for the ocean and wave modeling portion of the study.
When compared to existing and repeat measurements, the multibeam sonar data will also provide information on changes in seafloor topography between survey years within the region which can then be used to estimate sediment fluxes due to bedload transport. Approximately 224 km were surveyed during the 10-day cruise including lines previously surveyed for comparison between years.
A total of 18 seafloor samples were collected during the cruise using a “Ponar”-type grab.
The grab samples will be analyzed by UAA to determine sediment size distributions in the area for use in the modeling efforts in order to understand sediment transport within the bay. Multibeam acoustic backscatter measurements will also be calibrated against the in-situ seafloor sediment information so that maps of sediment size derived from the multibeam acoustic backscatter measurements can be created.
A sled-mounted Acoustic Doppler Current Profiler (ADCP) was towed alongside the survey vessel to measure water column velocity and acoustic backscatter. Approximately 167 km of ADCP surveys were completed during the cruise.
A met station was also installed on the southern coast of Foggy Island Bay to measure wind speed and direction, barometric pressure, temperature and relative humidity.
Two cameras mounted on the met station provide hourly images of the nearby coast for quantifying coastal change over the course of the project. The met-station and cameras will remain deployed for the duration of the field-portion of the project. In addition, a small drone was deployed to image coastal position and topography. Technical problems with the drone prevented a complete drone survey. A Spoondrift “spotter” buoy for measuring surface wave spectra in real-time could not be deployed this summer due to persistent ice in the region.
For more details on the 2018 Field Program, see the 2018 CBSWHMS Field Report
2018 Update on Dynamically Downscaled GCM and Reanalysis Hindcast and Forecast Products
Quality of the Dynamically Downscaled Reanalysis Winds
The wave models employed in this project require atmospheric forcing from reanalysis/modeled gridded data sets. The wave models require grid information specifically on wind speed and direction and sea ice. Available data sets for validating winds in northern Alaska are quite limited with few stations having long records suitable for analysis of climate variability. Remote sensing data is also highly limited for winds (limited to open water conditions in the case of QuikSCAT), therefore this study relies heavily on the use of global reanalysis and climate model data for the wind forcing data. For this study we have selected a domain that covers much of the Beaufort and Chukchi Seas to provide the model with sufficient fetch for the wind fields. The Chukchi-Beaufort High-Resolution Atmospheric Reanalysis (CBHAR) is the most comprehensive reanalysis with coverage over the area of interest in this study for 1979-2009.
The CBHAR will serve as the primary baseline for the analysis of the dynamically downscaled ERA-Interim used in this study. The key reasons for using the downscaled ERA-Interim and not CBHAR are that CBHAR covers a more limited area and does not include future climate scenarios required by our study. The sea ice concentration variable from the downscaling was prescribed in WRF from the ERA-Interim where it was directly interpolated from satellite observations (Dee et al. 2011), therefore no additional validation is required.
Preliminary analysis shows that the differences in monthly mean wind speeds are of 1 m/s or less over the Arctic ocean based on the 1979-2009 climatologies of the downscaled ERA and CBHAR. Analysis based on the monthly extremes based on the top 90th percentile of the monthly mean wind speeds shows differences less than 5% over the Foggy Island Bay ocean areas. Additional evaluation is planned for future publications and presentations on wind direction using coastal stations and buoy data.
For more information, please see our poster from AGU Fall Meeting 2018:
Status of Available Historical Observational Data
Barrow, Prudhoe Bay, Oliktok Point and Historical Seasonal Data from Resolution Island off Endicott Causeway
Wind roses have been created for the key stations at Barrow, Prudhoe (1993-2017), Oliktok (1978-1999) and Resolution Island (1986-1987, summer – fall seasonal only). Preliminary analysis shows generally consistent frequencies in wind direction and speed among the stations. Further analysis will soon be undertaken to evaluate the winds by season and for overlapping, consistent time periods for comparison to the shorter period seasonal data from Resolution Island.
To initiate quality control checking of these historical data, we plotted wind roses for the full dataset for each location. Barrow has the longest data set and covers the period of observations for all of the other sites.
The Prudhoe data show a relatively higher frequency of westerly winds, possibly due to the different time period of the data at this station compared to the Barrow record.
Regardless, the stations all share a similar frequency pattern of wind direction (most frequent are from the east). Now that Barrow and the date/time information is working properly our NCL software, we will be able to start producing plots for specific time periods/seasons for more accurate 1:1 comparisons between locations. Resolution Island and Oliktok Point sites maybe more influenced by sea breeze compared to winds from Deadhorse, and this will be investigated in 2019. Resolution Island definitely is illustrating seasonal dominance of easterly winds in summer-early fall.
2018 Update on Wave, Hydrodynamic and Sediment Transport Modeling
2018 Update on the Coastal Erosion Forecasting and Modeling
In order to support the sediment transport and shoreline change modeling and forecasting, sixteen sediment grab samples from the Foggy Island Bay seafloor were collected and analyzed for grain size distribution (See 2018 Field Campaign Summary above). Results are indicating the Foggy Island Bay seafloor is mainly fine sand. However, three samples were gravelly sand and two were silty sand. Analysis of a 2-liter sample of water found a total suspended sediment concentration of 0.031 g/liter, with a median grain size (d50) of 0.02 mm. [Note: Details of the water sample location, depth, and time of sampling provided in the April 2019 Annual Report].
Modeling of Coastal Erosion
The project scope includes the hindcasting and forecasting of shoreline change (i.e., coastal erosion) on decadal time scales as well as the modeling and forecasting of coastal geomorphic change and sediment transport during individual storm events. In order to achieve the long-term hindcasting and forecasting of shoreline change, researchers are developing a semi-empirical, “one-line” model using COSMOS software. The one-line model assumes that a single line, the shoreline, can explain coastal geomorphic change. As the shoreline advances or retreats (i.e., as the coast experiences accretion or erosion) the coastal morphology continues to maintain the equilibrium beach profile, and it shifts with the shoreline. COSMOS is an advanced, open source one-line model that allows for flexible parameter optimization, and the accommodation of Arctic-specific parameterizations.
Historic shoreline position data is critical for the development of predictive shoreline change models. Hence, in this project, we have emphasized the collection of shoreline position data through collaborations with Coastal Frontiers, BP, and Hilcorp Corporation.
The map here depicts some of the historic shoreline position data for a portion of the Foggy Island Bay coast at Point Brower, dating back to 1949.
In addition to the one-line modeling, the project is developing an Arctic-capable, process-based coastal geomorphic change model, focused on determining sediment transport and coastal change during individual storm events. Coastal processes in the Arctic differ from those in the non-Arctic because of the importance of both thermal and mechanical processes. In the Arctic, coastal soils and sediments are locked in place by permafrost or seasonal ice and thawing of that permafrost or ice is a prerequisite for mechanical removal. We have coupled a state-of-the-art, open-source geomorphic change model (Xbeach) with a thermal model accounting for heat transfer in Arctic settings.