The named region-scale indices, what each measures, what it needs as input,
and where the concept comes from. All are derived from gridded fields rather
than downloaded, which distinguishes them from the climate indices
datamatch::attach_climate_index() serves.
Usage
derived_indices(markdown = FALSE)
# S3 method for class 'derivoce_index_table'
print(x, ...)Value
a data frame of class derivoce_index_table, or a character string of
markdown when markdown = TRUE
Why three ways of measuring the same thing
Scotian Shelf inflow to the Gulf of Maine appears here three times, because the literature measures it three ways and they answer different questions.
A transport across a section measures the crossing itself, and is the only one that gives a direction and a flux. A water-mass fraction measures how much of the water present came from there, which is what matters for nutrients and is available even where velocities are not. A box anomaly measures the most visible consequence, freshening, and is the most robust to poor velocity data but the least specific about cause.
They disagree in informative ways. A strong inflow with a normal salinity anomaly means the arriving water was not unusually fresh, which is a real finding about the upstream shelf rather than a contradiction.
Examples
derived_indices()
#> Regional indices derivoce can compute
#> ----------------------------------------------------------------------
#> name method needs
#> scotian_shelf_inflow transport UO, VO
#> northeast_channel_inflow transport UO, VO
#> water_mass_fraction T-S endmember mixing SST, SSS, and two endmembers
#> eastern_gom_salinity box anomaly SSS
#> units
#> m^2/s
#> m^2/s
#> fraction, 0 to 1
#> PSU
#>
#> scotian_shelf_inflow
#> measures: Scotian Shelf Water crossing into the Gulf of Maine at Cape Sable
#> sign: positive into the Gulf of Maine
#> source: Feng et al. 2016; Wang et al. 2022
#>
#> northeast_channel_inflow
#> measures: slope water entering the Gulf of Maine through the Northeast Channel
#> sign: positive into the Gulf of Maine
#> source: Ramp et al. 1985; Du et al. 2022; Silver et al. 2023
#>
#> water_mass_fraction
#> measures: what fraction of each cell is a named water mass
#> sign: 1 is entirely the first endmember
#> source: Townsend et al. 2015
#>
#> eastern_gom_salinity
#> measures: freshening in the eastern Gulf of Maine, where inflow first appears
#> sign: negative is fresher, indicating stronger inflow
#> source: Grodsky et al. 2025
#>
#> Full descriptions: as.data.frame(derived_indices())$description
#> Markdown table: cat(derived_indices(markdown = TRUE))
cat(derived_indices(markdown = TRUE))
#> | Index | Measures | Method | Needs | Units | Source |
#> | --- | --- | --- | --- | --- | --- |
#> | `scotian_shelf_inflow()` | Scotian Shelf Water crossing into the Gulf of Maine at Cape Sable | transport | UO, VO | m^2/s | Feng et al. 2016; Wang et al. 2022 |
#> | `northeast_channel_inflow()` | slope water entering the Gulf of Maine through the Northeast Channel | transport | UO, VO | m^2/s | Ramp et al. 1985; Du et al. 2022; Silver et al. 2023 |
#> | `water_mass_fraction()` | what fraction of each cell is a named water mass | T-S endmember mixing | SST, SSS, and two endmembers | fraction, 0 to 1 | Townsend et al. 2015 |
#> | `eastern_gom_salinity()` | freshening in the eastern Gulf of Maine, where inflow first appears | box anomaly | SSS | PSU | Grodsky et al. 2025 |