day22_antarctica.R

library(rnaturalearth)
library(rnaturalearthdata)
library(mapgl)
library(mapview)
library(sf)
library(dplyr)

antartic10 <- ne_download(scale = 50, type = 'antarctic_ice_shelves_polys', 
                       category = 'physical')
antartic10l <- ne_download(scale = 50, type = 'antarctic_ice_shelves_lines', 
                          category = 'physical')

# create polygon representing "WGS 84 / Antarctic Polar Stereographic EPSG:3031"
bb <- st_polygon(x = list(
  matrix(
    c(
      -180.0, -90.0,
      180, -90,
      180, -60,
      -180, -60,
      -180, -90),
    ncol=2,
    byrow=TRUE)
)
) |>
  st_sfc(crs = 4326) |>
  st_as_sf()
# need attributes to work in mapboxgl
bb$name <- "WGS 84 / Antarctic Polar Stereographic EPSG:3031"
mapboxgl_view(bb)

# https://en.wikipedia.org/wiki/South_Pole
# South Geographic Pole
south_pole_1 <- st_point(x = c(0, -85)) |> st_sfc(crs = 4326) |>
  st_as_sf()
south_pole_1$name <- "South Geographic Pole"
maplibre_view(south_pole_1)
mapview(south_pole_1)
# South Magnetic Pole (2020)
south_pole_2 <- st_point(x = c(135.866, -64.081)) |> st_sfc(crs = 4326) |> 
  st_as_sf()

maplibre(style = carto_style("voyager"),
         projection = "globe") |> 
  fit_bounds(antartic10) |> 
  add_fill_layer(id = "EPSG:3031",
                 source = bb,
                 fill_opacity = 0.5,
                 fill_color = "lightgrey"
                 ) |> 
  add_fill_layer(id = "glaciated areas",
                source = glacial,
                fill_color = "scalerank") |> 
  add_fill_layer(id = "polys",
                 source = antartic10,
                 fill_color = "orange") |> 
  add_line_layer(id = "lines",
                 source = antartic10l,
                 line_color = "red",
                 line_width = 3) |> 
  add_circle_layer(id = "South Geographic Pole",
                   source = south_pole_1,
                   circle_color = "lightblue") |> 
  add_circle_layer(id = "South Magnetic Pole (2020)",
                   source = south_pole_2,
                   circle_color = "navy") |> 
  add_legend(legend_title = "Antarctic Ice Shelves",
             type = "categorical",
             values = c("Ice shelf collapses", 
                        "Ice shelf previous extent",
                        "Antarctic Polar Stereographic",
                        "Almost the South Pole (0, -85)",
                        "South Magnetic Pole (2020)"),
             colors = c("orange", "red", "lightgrey", "lightblue", "navy"),
             style = list(
               background_opacity = 0.95,
               background_color = "#2E8B57",
               text_color = "white",
               border_width = 1,
               border_color = "gray",
               title_color = "white",
               element_border_color = "white",
               element_border_width = 1
             )) |> 
  add_control("<div style='padding: 5px; background-color: #2E8B57; color: white;'>
              <h2>Antarctic Ice Shelves</h2>
              Derived from 2003-2004 Mosaic of Antarctica<br />
              WGS 84 / Antarctic Polar Stereographic EPSG:3031 limit<br />
              Day 22: Natural Earth<br />
              data: <a href='https://www.naturalearthdata.com/downloads/10m-
              physical-vectors/10m-antarctic-ice-shelves'
              style='text-decoration:none;color:lightblue'>10m-antarctic-ice-shelves</a><br />
              𝚖𝚊𝚌𝚔𝚊 𝚜𝚣𝚎𝚌𝚑𝚗𝚘<br />22 November 2025
              </div>",
              position = "top-right")