7 Bottom temperature - High Resolution
Description: Seasonal bottom temperatures on the Northeast Continental Shelf between 1959 and 2022 in a 1/12° grid.
Indicator category: Published Methods, Synthesis of published information
Found in: State of the Ecosystem - Gulf of Maine & Georges Bank (2023+); State of the Ecosystem - Mid-Atlantic Bight (2023+)
Contributor(s): Joe Caracappa, Hubert du Pontavice, Vincent Saba, Zhuomin Chen
Data steward: Joe Caracappa, joseph.caracappa@noaa.gov
Point of contact: Joe Caracappa, joseph.caracappa@noaa.gov
Public availability statement: Source data are NOT publicly available. Please email hubert.dupontavice@noaa.gov for further information and queries of bottom temperature source data.
7.1 Methods
7.1.1 Data sources
7.1.1.1 Study area
The bottom temperature product covered the northeast U.S. shelf marine ecosystem (NEUS) and specifically an area of four Ecological Production Units (EPUs) defined by NOAA’s Northeast Fisheries Science Center (https://noaa-edab.github.io/tech-doc/epu.html).
7.1.1.2 Design of the gridded bottom temperature time series
The bottom temperature product is in a horizontal 1/12 degree grid between 1959 and 2022 and is made of daily bottom temperature estimates from:
Bias-corrected ROMS-NWA (ROMScor) between 1959 and 1992 which was regridded in the same 1/12degree grid as GLORYS using bilinear interpolation; GLORYS12v1 in its original 1/12 degree grid between 1993 and 2020; GLO12v3 (called PSY4V3R1 in “A High-Resolution Ocean Bottom Temperature Product for the Northeast u.s. Continental Shelf Marine Ecosystem” (2023) and Lellouche et al. (2018)) in its original 1/12 degree grid for 2021. GLO12v4 in its original 1/12 degree grid for 2022.
7.1.1.3 Ocean model data
Four ocean models were used to get high-resolution daily bottom temperature on the NEUS between 1959 and 2022.
For the period between 1959 and 1992, we used daily ocean bottom temperature from the long-term (1958–2007) high-resolution numerical simulation of the Northwest Atlantic Ocean in the Regional Ocean Modelling System (ROMS), a split-explicit, free-surface, terrain-following, hydrostatic, primitive equation model (Shchepetkin and McWilliams (2005)). The model domain covers the Northwest Atlantic Ocean with ~7km horizontal resolution and 40 vertical terrain- following layers. A detailed description of ROMS-NWA can be found in Chen et al. (2018a).
For the period between 1992 and 2020, the daily bottom temperature outputs from the GLORYS12v1 ocean reanalysis product were used. GLORYS12v1 is a global ocean, eddy-resolving, and data assimilated hindcast from Mercator Ocean (European Union-Copernicus Marine Service, 2018; Fernandez and Lellouche2018; Jean-Michel et al. (2021a)) with 1/12 degree horizontal resolution and 50 vertical levels. The base ocean model is the Nucleus for European Modelling of the Ocean 3.1 (NEMO 3.1; Madec, 2016) driven at the surface by the European Centre for the Medium-Range Weather Forecasts (ECMWF) ERA-Interim reanalysis (Dee et al. (2011)). Remotely sensed and in situ observations are jointly assimilated by means of a reduced-order Kalman filter.
For the year 2021 and 2022, we used GLO12v4 which is a revised and updated version of GLO12v3 (European Union-Copernicus Marine Service, 2016). The general model structure is similar to GLO12v3 with some changes in model configuration, parameterizations, relaxations to avoid spurious drifts, river inputs, atmospheric fluxes and data assimilation (more detail in https://data.marine.copernicus.eu/product/GLOBAL_ANALYSISFORECAST_PHY_001_024/description)
7.1.1.4 Bias-correction process of NWA-ROMS
We used the methodology presented in du Pontavice et al. (2023) based on the Northwest Atlantic Regional Ocean Climatology (NWARC). The first step was to regrid ROMS-NWA bottom temperature over the same 1/10 degree horizontal grid as the NWARC using bilinear interpolation. Then, we conducted the bottom temperature bias-correction in the 1/10 degree NWARC grid using monthly climatologies from NWARC over four decadal periods from 1955 to 1994. A monthly bias was calculated in each 1/10 degree grid cell and for each decade (1955–1964, 1965–1974, 1975–1984, 1985–1994). Based on this monthly bias, we estimated a daily bias for each decade in each grid cell. Lastly, for each ROMS-NWA grid cell we identified the bias from the closest 1/10 degree NWARC grid cell and subtracted the daily bias to the daily ROMS-NWA bottom temperature for all years and days of each decade.
7.1.2 Data processing
Derived bottom temperature data were formatted for inclusion in the ecodata R package using the R code found here.
catalog link https://noaa-edab.github.io/catalog/bottom_temp_seasonal_gridded.html