How can city governments plan for the effects of sea level rise? A new tool developed by NASA’s Jet Propulsion Lab incorporates claims to include all factors that affect sea level rise for multiple points around the globe, tailoring predictions to projected local conditions in a particular time period.

Polar and glacial ice melting into the world’s oceans greatly contributes to sea level rise. Loss of land ice alsoThe gradient of sea level rise near New York City with respect to ice loss from the Greenland Ice Sheet. Red indicates a larger impact on NYC local sea level rise. Source: NASA/JPL-Caltech affects Earth’s gravitational and rotational potentials, which in turn results in spatial patterns of sea level rise — called sea-level footprints. Predicting future ice loss, not only the gross amount but the specific locations and amount of ice lost in these areas, is a critical but previously unavailable element of sea-level rise modeling.

For example, predictions of the effects of the submarine ice sheet collapse of the West Antarctic Ice Shelf, averaged across the globe, is considerably less (25 percent) than predicted sea-level rise on both coasts of North America. Modeling tools currently available lack the level of granularity needed to calculate changes in the cryosphere through time and predict both singular events — an ice sheet collapse — and incremental ice loss over time.

The JPL team (Eric Larour, Erik R. Ivins and Surendra Adhikari) applied a mathematical technique common in other earth-science fields, combined with information from the Ice Sheet System Model, to obtain sea-level fingerprints. Their goal is to obtain “actionable signals of local sea-level change.” The improved understanding of the connection between global changes in ice cover and sea-level rise at port cities around the world would give policymakers accurate information on which to base planning decisions.

The new modeling technique, Gradient Fingerprint Mapping, predicts that ice melting in northwest Greenland will impact sea level around London. Ice melt from the northern half of Greenland will affect New York City. If ice melt speeds up or slows down in these locations, the new information will be fed into the model to update predictions.

The scientists reported their research in Science Advances on November 15, 2017. An interactive data visualization tool allows users to check predicted sea level rise in multiple coastal cities worldwide.