Author: Michael Sumner
Date: 2021-05-04

# Southern Ocean Fronts for R

#### Michael Sumner

#### 2021-05-04

## Orsi fronts for R

The “Orsi fronts” are a commonly used climatological map of Southern Ocean frontal distributions, once published on a Southern Ocean Atlas Database Page after Orsi et al. (1995).

The data is provided in this package as a built-in data set. The object `orsifronts` is a ‘SpatialLinesDataFrame’ object, as defined in the ‘sp’ package. (A ‘SpatialLinesDataFrame’ is a “GIS vector” layer where complex line geometry objects are linked to simple attribute data in a table form, and it behaves like a ‘data.frame’).

    library(orsifronts)
    #> Loading required package: sp
    cols <- hcl(seq(0, 240, length = nrow(orsifronts)), c = 50)
    plot(orsifronts, col = cols, lwd = 2)
    degAxis(1)
    degAxis(2)
    box()

There are 5 line objects, with some simple names and codes.

    as.data.frame(orsifronts)
    #>                                                         name front
    #> stf                                        Subtropical front   stf
    #> saf                                       Subantarctic front   saf
    #> pf                                               Polar front    pf
    #> saccf           Southern Antarctic circumpolar current front saccf
    #> sbdy  Southern Boundary of the Antarctic circumpolar current  sbdy
    plot(orsifronts, xlim = c(60, 180), col = cols, asp = 1/cos(55 * pi / 180), lwd = 4)
    legend("topleft", sprintf("%s (%s)", orsifronts$front, orsifronts$name),
           col = cols, lwd = 4, cex = 0.8, bty = "n")
    degAxis(1)
    degAxis(2)
    box()

## Park/Durand fronts for R

Similarly for the more recent Park/Durand fronts derived from altimetry remote sensing.

    as.data.frame(parkfronts)
    #>                                     name front
    #> 1                      Northern Boundary    NB
    #> 2                           Subantarctic   SAF
    #> 3                                  Polar    PF
    #> 4 Southern Antarctic Circumpolar Current SACCF
    #> 5                      Southern Boundary    SB
    pcols <- hcl(seq(0, 240, length = nrow(parkfronts)), c = 50)
    plot(parkfronts,col = pcols, asp = 1/cos(55 * pi / 180), lwd = 4)
    legend("topleft", sprintf("%s (%s)", parkfronts$front, parkfronts$name),
           col = cols, lwd = 4, cex = 0.8, bty = "n")
    degAxis(1)
    degAxis(2)
    box()

# References

Orsi, A. H., T. Whitworth III and W. D. Nowlin, Jr. (1995). On the meridional extent and fronts of the Antarctic Circumpolar Current, Deep-Sea Research I, 42, 641-673.