Make all urls for sea ice data
Examples
if (FALSE) { # \dontrun{
# Get all urls
seaiceeurls()
# for some range of years
seaiceeurls(yr = 1980:1983)
seaiceeurls(yr = 1980, mo = c("Jan", "Feb", "Mar"))
seaiceeurls(yr = 1980:1983, mo = c("Jan", "Apr", "Oct"))
# Get urls for Feb of all years, both S and N poles
seaiceeurls(mo='Feb')
# Get urls for Feb of all years, just S pole
seaiceeurls(mo='Feb', pole='S')
# Get urls for Feb of 1980, just S pole
seaiceeurls(yr=1980, mo='Feb', pole='S')
# GeoTIFF
seaiceeurls(yr=1980, mo='Feb', pole='S', format = "geotiff")
} # }