Quantifying contributions from glaciers and terrestrial hydrology to recent and future sea level change

PI: David Rounce

Co-Is/Collaborators:

Regine Hock, Mark Fahnestock, Richard Lammers, Danielle Grogan, Alex Prusevich, Bryant Loomis

Background:

Changes in total water storage, referring to changes in glaciers (excluding the ice sheets) and land water storage, is a major contributor to sea level change. Glaciers currently contribute about 1 mm per year (about 30% of present-day sea level rise), and projections estimate this may approach 3 mm per year by 2100. Land water storage, on the other hand, is the most uncertain component of the sea-level budget varying from +0.3 mm per year based on global models to -0.2 mm per year based on satellite observations. This uncertainty stems from (i) observations being unable to separate the glacier mass change from the land water storage signal and (ii) model uncertainty associated with precipitation data and models poorly accounting for important processes like groundwater, soil moisture, and human factors including irrigation. Our work will explicitly integrate the glaciers’ interaction with the hydrologic cycle and account for critical human factors to more accurately partition and quantify the contributions of glaciers and various hydrologic processes to sea level change.

Expected Significance

Our work will quantify the contribution of total water storage on land to global mean sea level change from 1950-2100, and distinguish its two components: glacier mass change and land water storage change. We will use a suite of remote sensing data and observations to better model the processes affecting glacier mass and land water storage changes including direct human intervention in the hydrologic cycle and responses to climate change. By explicitly linking our glacier and hydrologic models, our estimates of the glaciers’ contribution to sea level rise will be the first set of glacier projections that has accounted for glacier runoff in endorheic basins that never reaches the ocean and for the complex interactions of glaciers and terrestrial hydrology that may include losses to evapotranspiration from irrigation, evaporation from reservoirs, and groundwater recharge. The resulting projections of the contribution of glaciers and land water storage to sea level change will directly support the NASA SLCT’s sea level change projections and various assessment frameworks like the IPCC.

Objectives

1. Quantify the effects of changing glaciers and land water storage on global mean sea level change by refining and integrating glacier and hydrologic models.

2. Determine the underlying physical mechanisms affecting both glacier mass change, land water storage, and the linkage between the two.

Deliverables

Datasets

• Glacier and land water storage contributions to sea level change from 1950 – 2100

• River discharge and temperature for coastal regions from 1950 - 2100

• Glacier-wide mass balances from ICESat-2

• Glacier frontal ablation and debris thickness estimates

• Glacier model: Python Glacier Evolution Model (PyGEM)

• Hydrologic model: Water Balance Model (WBM)

Datasets Used

Digital Elevation Models (SRTM, TanDEM-X, ASTER), Optical satellite imagery (Landsat, Sentinel, ASTER), Gravimetric satellite observations (GRACE, GRACE-FO), Satellite altimetry (ICESat-2), In-situ glacier mass balance measurements, Climate data (ERA5, CMIP5, CMIP6), Hydro-infrastructure datasets, Global runoff data (GRDC)