- Ice Sheet Freshwater Forcing
- Introduction
- Workshop
- Data Products
This repository contains discussions and workbooks (code) from a virtual workshop on Anomalous Freshwater Fluxes.
Included in this repository are:
- GitHub Discussions from before, during, and after the workshop.
- Workbooks (code) used to build data products (e.g. Greenlandic and Antarctic freshwater from surface melt, ice shelf melt, basal melt, icebergs, etc.).
- Examples of data product post-processing to aid modelers who want use the data.
The virtual workshop on Anomalous Freshwater Fluxes aimed to capture freshwater fluxes from ice sheets and ice shelves for use in climate models that don’t include interactive ice sheets. The workshop slides, videos, and discussion notes are archived at https://zenodo.org/doi/10.5281/zenodo.11127902.
To stay up-to-date with existing and new discussions, click on the watch button near the top of this page and then select All Activity or Custom > Discussions (and Issues). If you’re new to GitHub, it can be used as a collaborative project management tool (in addition to a code repository). See Braga (2023) http://doi.org/10.1111/2041-210x.14108.
There are two types of data products provided here:
- Freshwater volume flow rate [units: Gt/yr or m^3/s] with a geospatial component of where this freshwater enters the ocean. The geospatial component is a region of interest (ROI) such as `NE` or `SW` for Greenland, or sector number (1 through 18) for Antarctica.
- Weighted freshwater distribution maps [units: m-2]. These are maps of where freshwater is distributed within a ROI if not at the coast, for example iceberg melt. These maps are provided in EPSG:4326 (lon,lat) projection.
| Filename | Dimensions | Description |
|---|---|---|
| AQ_calving.nc | region, time | Antarctic ice shelf calving |
| AQ_subshelf_melt.nc | region, time | Antarctic ice shelf basal melting |
| AQ_iceberg_melt.nc | lon, lat | Antarctic iceberg melt by location and magnitude |
| GL_discharge.nc | region, time | Greenland ice sheet discharge upstream from grounding line |
| GL_runoff.nc | region, time | Greenland ice sheet and non-ice grounded liquid runoff |
| GL_basal_melt.nc | region | Greenland grounded ice basal melt by region |
| GL_iceberg_melt.nc | lon, lat, time | Greenland iceberg melt magnitude by month and location |
All products below are split by the Rignot (2017) regions a.k.a. IMBIE 2 regions.
- Workbook: ./AQ_subshelf_melt.org
Average of sub-shelf melt estimates from Davison (2023) and Paolo (2024; dataset)
<xarray.Dataset> Size: 5kB
Dimensions: (time: 31, region: 18)
Coordinates:
* time (time) datetime64[ns] 248B 1991-07-01 1992-07-01 ... 2021-07-01
* region (region) int32 72B 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Data variables:
melt (region, time) float64 4kB ...
region_name (region) <U5 360B ...
Attributes:
description: Antarctic region sub-shelf melt
date_created: 20241101T045557Z
title: Subshelf melt per region
history: Processed for Schmidt (YYYY; in prep); by Ken Mankoff
source: doi:10.5067/SE3XH9RXQWAM and doi:10.5281/ZENODO.8052519
Conventions: CF-1.8
DOI: https://doi.org/10.5281/zenodo.14020895
- Workbook: ./AQ_calving.org
Antarctic iceberg calving estimates from Davison (2023)
<xarray.Dataset> Size: 8kB
Dimensions: (region: 18, time: 25)
Coordinates:
* time (time) datetime64[ns] 200B 1997-07-01 1998-07-01 ... 2021-07-01
* region (region) int32 72B 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Data variables:
calving (region, time) float64 4kB ...
uncertainty (region, time) float64 4kB ...
region_name (region) <U5 360B ...
Attributes:
description: Antarctic region ice shelf calving rate
date_created: 20241101T153743Z
title: Calving per region
history: Processed for Schmidt (YYYY; in prep); by Ken Mankoff
source: doi:10.5281/ZENODO.8052519
Conventions: CF-1.8
DOI: https://doi.org/10.5281/zenodo.14020895
Normalized iceberg melt patterns per region of origin, i.e. for calving in 18 Antarctic-IMBIE2 regions. From a circum-Antarctic 0.25° simulation forced by the recommended normal year of JRA55 repeated 30 years after spin up. The simulation only covers south of 52.25°S, so a part of the melt pattern is missing (11% missing based on Mathiot and Jourdain 2023).
<xarray.Dataset> Size: 238MB
Dimensions: (time: 12, region: 18, latitude: 360, longitude: 720)
Coordinates:
* longitude (longitude) float64 6kB -179.8 -179.2 -178.8 ... 179.2 179.8
* latitude (latitude) float64 3kB -89.75 -89.25 -88.75 ... 89.25 89.75
* region (region) int32 72B 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
* time (time) int8 12B 1 2 3 4 5 6 7 8 9 10 11 12
spatial_ref int8 1B ...
Data variables:
melt (time, region, latitude, longitude) float32 224MB ...
melt_AQ (time, latitude, longitude) float32 12MB ...
msk_nemo (latitude, longitude) float32 1MB ...
region_name (region) <U5 360B ...
region_map (latitude, longitude) int16 518kB ...
Attributes: (12/13)
description: Annual JRA55 climatology
original_data: NEMO 0.25° simulations by Anna Olive-Abello (in prep...
script_used: remap_per_basin.py
processed_by: Nicolas Jourdain <nicolas.jourdain@univ-grenoble-alp...
geospatial_lat_min: -89.75
geospatial_lat_max: 89.75
... ...
geospatial_lon_max: 179.75
date_created: 20241117T141200Z
title: Normalised iceberg melt climatology in the Southern ...
history: Processed for Schmidt (YYYY; in prep); by Ken Mankoff
Conventions: CF-1.8
DOI: https://doi.org/10.5281/zenodo.14020895
- Minimal and only on the peninsula. Not done as part of this work.
- Small term (~70 Gt yr-1 per van Liefferinge (2013), not done as part of this work.
All products below are split by the Mouginot (2019) regions
This data product is MAR runoff distributed into Mouginot (2019) http://doi.org/10.7280/d1wt11 regions, but processed at stream level by Mankoff (2020) http://doi.org/10.5194/essd-12-2811-2020. The data includes ‘ice runoff’ which comes from melted ice, snow, and rain on the ice sheet, and ‘land runoff’ which comes from melted snow and rain on land. Runoff is routed through individual streams (subglacial for ice, sub-aerial for land). Both ice-sourced and land-sourced runoff can enter the ocean either at the surface (from a terrestrial stream) or at depth subglacially. This value is estimated per stream. When summing subglacial discharge by ROI, the minimum submarine discharge depth is provided for each ROI.
- Workbook: ./GL_runoff.org
- Data product:
GL_runoff.nc
<xarray.Dataset> Size: 203kB
Dimensions: (region: 7, time: 876)
Coordinates:
* region (region) int32 28B 1 2 3 4 5 6 7
* time (time) datetime64[ns] 7kB 1950-01-01 ... ...
Data variables:
subglacial_discharge_from_land (region, time) float64 49kB ...
surface_runoff_from_land (region, time) float64 49kB ...
subglacial_discharge_from_ice (region, time) float64 49kB ...
surface_runoff_from_ice (region, time) float64 49kB ...
min_discharge_depth (region) float32 28B ...
region_name (region) <U2 56B ...
Attributes:
title: Ice sheet runoff by Mougniot region
history: TBD
Conventions: CF-1.8
DOI: https://doi.org/10.5281/zenodo.14020895
This product is generated from flux gates ~5 km upstream of the terminus.
It lacks:
- Terminus retreat, which should add ~10 % over the last two decades
- Splitting output between icebergs and submarine melt, which is ~50 % +- 40 % (Enderlin 2013)
- Workbook: ./GL_discharge.org
- Data product:
GL_discharge.nc
<xarray.Dataset> Size: 12kB
Dimensions: (region: 7, time: 185)
Coordinates:
* region (region) int32 28B 1 2 3 4 5 6 7
* time (time) datetime64[ns] 1kB 1840-01-01 1841-01-01 ... 2024-01-01
Data variables:
discharge (region, time) float32 5kB ...
err (region, time) float32 5kB ...
region_name (region) <U3 84B ...
Attributes: (12/14)
featureType: timeSeries
title: Greenland ice sheet discharge by Mougniot region
summary: Greenland ice shet discharge by Mougnito region
keywords: Greenland; Mass; Mass balance
source: git commit: 20af941
creator_name: Ken Mankoff
... ...
institution: NASA GISS
references: TBD
product_version: 1.0
history: TBD
Conventions: CF-1.8
DOI: https://doi.org/10.5281/zenodo.14020895
This dataset provides spatial maps of iceberg meltwater based on iceberg source. Maps are weighted masks where each region sums to one, plus one all-Greenland weighted map.
- Workbook: ./GL_iceberg_melt.org
- Data product:
GL_iceberg_melt.nc
<xarray.Dataset> Size: 177MB
Dimensions: (region: 7, time: 12, longitude: 720, latitude: 360)
Coordinates:
* region (region) int8 7B 1 2 3 4 5 6 7
* time (time) int8 12B 1 2 3 4 5 6 7 8 9 10 11 12
* longitude (longitude) float64 6kB -179.8 -179.2 -178.8 ... 179.2 179.8
* latitude (latitude) float64 3kB -89.75 -89.25 -88.75 ... 89.25 89.75
Data variables:
melt (region, time, latitude, longitude) float64 174MB ...
melt_GL (latitude, longitude) float64 2MB ...
region_map (latitude, longitude) int8 259kB ...
region_name (region) <U2 56B ...
spatial_ref int8 1B ...
Attributes:
geospatial_lat_min: -90
geospatial_lat_max: 90
geospatial_lon_min: -180
geospatial_lon_max: 180
date_created: 20241117T144923Z
title: Normalised iceberg melt climatology per region of ca...
history: Processed for Schmidt (YYYY; in prep); by Ken Mankoff
Conventions: CF-1.8
DOI: https://doi.org/10.5281/zenodo.14020895
This product splits basal melt from Karlsson (2021) http://doi.org/10.1038/s41467-021-23739-z into regions, with two products per region: Water that enters fjords at their surface from sub-aerial streams, and water that enters subglacially.
- Workbook: ./GL_basal_melt.org
- Data product:
GL_basal_melt.nc
