Table of contents

• Introduction
• Info
• Data
  • Antarctica
  • Greenland
• Mask
  • 288x180

Introduction

Generate freshwater anomaly data files and distribution mask for ModelE

• Anomaly is defined as mass loss from grounded ice and ice shelves (but not sea ice) since 1990.
• Spatially, ModelE distributes a single value according to a ‘distribution field’ - a floating point mask that sums to 1.

See ./workbook.org for a digital workbook.

Info

• Contact: Ken Mankoff <ken.mankoff@nasa.gov>
• Code: https://github.com/NASA-GISS/freshwater-anomaly
• Data: Mankoff et al. (2021) and Slater et al. (2021)

Data

Antarctica

head out/mass_change_antarctica.csv

# Contact: Ken Mankoff <ken.mankoff@nasa.gov>
# Code: https://github.com/NASA-GISS/freshwater-anomaly
# Data: Slater /et al./ (2021)
# Summary: Annual mass loss from Antarctica.
# Year	Gt/yr
1990	115.8
1991	115.8
1992	115.8
1993	115.8
1994	115.8

Notes

• Time series extended back and forward from data range to 1990-2019 using average of first or last three years of data
• _hi and _lo are +- mean 66 Gt/yr, max 72 Gt/yr, and sum 198 Gt/yr
  • This comes from published Slater et. al (2021) uncertainties, assuming 1 σ uncertainty in Table 1 for ice shelf thinning, ice shelf calving, and Antarctic grounded ice.

Greenland

head out/mass_change_greenland.csv

# Contact: Ken Mankoff <ken.mankoff@nasa.gov>
# Code: https://github.com/NASA-GISS/freshwater-anomaly
# Data: Mankoff /et al./ (2021)
# Summary: Annual mass change from Greenland.
# Year	Gt/yr
1990	137.6
1991	76.7
1992	-87.1
1993	90.7
1994	113.8

Notes

• mass_change_no_gain_greenland.csv is same as mass_change_greenland.csv, but years with mass gain spread over following year(s) with loss so values always positive (mass loss)
• Use uncertainty from citet:mankoff_2021 published with data
• Use published (1 σ) uncertainty because that uncertainty treatment is already conservative and if using 2 σ, mass gain occurs most year for lo estimates

Mask

288x180

• 1/8th degree distribution mask
• Buffers at 50, 100, 250, and 500 km

ncdump -chs out/fw_288x180.nc

netcdf fw_288x180 {
dimensions:
	lat = 180 ;
	lon = 288 ;
variables:
	double crs(lat, lon) ;
		crs:_FillValue = NaN ;
		crs:grid_mapping_name = "latitude_longitude" ;
		crs:grid_mapping = "crs" ;
	double ones_050(lat, lon) ;
		ones_050:_FillValue = 0. ;
		ones_050:description = "Grid cells w/in 050 km of coast with freshwater runoff, submarine melt, or iceberg forcing" ;
		ones_050:grid_mapping = "crs" ;
	double ones_100(lat, lon) ;
		ones_100:_FillValue = 0. ;
		ones_100:description = "Grid cells w/in 100 km of coast with freshwater runoff, submarine melt, or iceberg forcing" ;
		ones_100:grid_mapping = "crs" ;
	double ones_250(lat, lon) ;
		ones_250:_FillValue = 0. ;
		ones_250:description = "Grid cells w/in 250 km of coast with freshwater runoff, submarine melt, or iceberg forcing" ;
		ones_250:grid_mapping = "crs" ;
	double ones_500(lat, lon) ;
		ones_500:_FillValue = 0. ;
		ones_500:description = "Grid cells w/in 500 km of coast with freshwater runoff, submarine melt, or iceberg forcing" ;
		ones_500:grid_mapping = "crs" ;
	double lat(lat) ;
		lat:_FillValue = NaN ;
		lat:units = "degrees_north" ;
	double lon(lon) ;
		lon:_FillValue = NaN ;
		lon:units = "degrees_east" ;

// global attributes:
		:Creator = "Ken Mankoff" ;
		:email = "ken.mankoff@nasa.gov" ;
		:source = "https://github.com/NASA-GISS/freshwater-anomaly" ;
		:_Format = "classic" ;
}