R/get_sea_level.R

In pastclim: Manipulate Time Series of Climate Reconstructions

#' Get sea level estimate
#'
#' This function returns the estimated sea level from Spratt et al. 2016, using
#' the long PC1. Sea levels are from contemporary sea level (note that the
#' original data are with reference to the sea level during the Holocene ~5k
#' year ago).
#'
#' @param time_bp the time of interest
#' @returns a vector of sea levels in meters from present level
#'
#' @keywords internal


get_sea_level <- function(time_bp) {
  # get sea level from Spratt 2016
  sea_level_info <- utils::read.table(
    system.file("extdata/sea_level_spratt2016.txt",
      package = "pastclim"
    ),
    header = TRUE
  )
  time_calkaBP <- -time_bp / 1000 # nolint
  if (any(time_calkaBP < 0)) {
    stop("this function only supports times in the past")
  }
  if (any(time_calkaBP > 798)) {
    stop("the dataset of sea level reconstructions stops at 798ky BP")
  }
  ## TODO this is not safe, we should be getting the closest values
  ## or even better interpolate
  sea_level <- stats::approx(
    x = sea_level_info$age_calkaBP,
    y = sea_level_info$SeaLev_longPC1,
    xout = time_calkaBP
  )$y
  # rescale to have 0 for 0kBP
  sea_level <- sea_level - sea_level_info$SeaLev_longPC1[1]
  return(sea_level)
}