Satellites track dwindling ice and rising seas, and scientists comb through the data. Then they run computer models to sharpen the picture: These accelerating changes will transform planet Earth.
The variety of talks and presentations at the 2019 American Geophysical Union conference in San Francisco was dizzying, but many hit on the theme of a changing planet. For the NASA Sea Level Change Team, the focus was on increasingly robust data sets, more accurate modeling, and a fuller accounting of all the factors that contribute to sea level rise.
The team’s talks over the five-day conference can be grouped into a few broad categories: physical mechanisms, observed changes, and projections. Knowledge in all three of these spheres is growing deeper and more crisply detailed.
“The presentations at the Fall AGU meeting demonstrated the breadth of work being done by the team,” said team leader Ben Hamlington of NASA’s Jet Propulsion Laboratory in Pasadena, California. “We are focused on understanding the drivers of regional relative sea-level rise, which really requires the broad range of expertise that was on display.”
Under the “physical mechanisms” category we might place a talk by John Fasullo from the National Center for Atmospheric Research in Boulder, Colorado. The talk was based on recent work by Fasullo and Steve Nerem of the University of Colorado. They considered simulations of sea-level rise across geographic regions during the 28-year satellite record, the period during which satellites have been capable of measuring sea-surface height.
Patterns of change
The simulations were run on sophisticated computer models, with and without the influence of humanity’s emissions of greenhouse gases and suspended particles, or aerosols. They found that the spatial patterns of sea-level rise during this period were largely driven by human emission of greenhouse gases and aerosols. They also showed that each type of emission is responsible for its own distinct pattern of change in sea level. And they found that such detectable patterns, especially for aerosols, probably predated the satellite era, likely causing a skew in interpretation of tide-gauge readings for at least half a century – including an overestimate of the mean rate of sea-level rise and an underestimate of its recent acceleration.
“Going forward through 2050, each of these agents will drive a distinct pattern of rise (depending on what your emissions eventually are) and thus will provide some degree of predictability to the regional character of sea level rise,” Fasullo wrote in an email.
“Observed changes” could include a talk by Carmen Boening of NASA’s Jet Propulsion Laboratory in Pasadena, California. She summarized her earlier findings that were something of a first for sea-level science. Using data from NASA’s GRACE satellites (Gravity Recovery and Climate Experiment), Boening showed that a temporary, 5-millimeter drop in global mean sea level in 2010-11 was caused by water storage on land – a La Niña-driven shift to greater rainfall over Australia, northern South America and Southeast Asia.
And for “projections,” we might turn to a presentation by Benjamin Strauss of Climate Central. He was introducing a new, publicly available online tool, partly funded by NASA, allowing users to generate maps of coastal flood vulnerability almost anywhere in the world. The map is based on an analysis presented in another AGU talk by Scott Kulp, a senior computational scientist at Climate Central. The map uses Google Earth as a platform, and can range across time-frames with varying assumptions. The map also can incorporate sea-level projections and flooding events. It is likely to be the first freely available, interactive map of its kind.
These are just a few examples of the 40 talks or poster sessions by members of the NASA Sea Level team. Please see the accompanying sidebar for the full list.
AGU Conference talks and poster sessions from the NASA Sea Level Science Team, 2019
Thomas Frederikse: “Revisiting the Contemporary Sea-level Budget in Light of Land Mass Changes and Ocean Heat Uptake” (poster session)
Zhuoya He: “Reconstruction of 36-Year Measurement-based Sea-level Fingerprints from Land Ice Mass Changes” (poster session)
Steve Nerem: “Extrapolating Satellite Data Records for Short-Term Regional Sea Level Projections: Understanding the Contributions of Forcing Agents” (poster session)
Nicole Schlegel: “Bedrock Topography Requirements for Reducing Uncertainties in Ice Sheet Model Projections of Century-scale Antarctic Sea-level Contribution” (poster session)
John Fasullo: “Drivers of the Altimeter Era Forced Response in Regional Sea Level and Consequences for the Coming Decades”
Fernando Paolo: “Next Generation Estimates of Antarctic Ice Shelf Melt Rates”
Manoochehr Shirzaei: “Unprecedented Crop Loss Due to 2019 Midwest US Flood Quantified from Space”
Jerry X. Mitrovica: “Assessing Sea-level Risk and Coastal Resilience in a Progressively Warming World”
Eric Larour: “Antarctica Slowdown from Solid Earth and Sea-level Negative Feedbacks”
Evelyn M. Powell: “Investigating the Bias in GPS-derived 1-D Viscosity Models due to Antarctica’s Complex 3-D Mantle Structure”
Robert Kopp: “Uncertainty and Ambiguity in Future Mean and Extreme Sea-level change”
Surendra Adhikari: “Towards Explaining the Causes of GPS-derived Crustal Uplift Rates in Greenland”
Sophie Nowicki: “Projections of 21st Century Sea-level Change from the Ice Sheet Model Intercomparison Project for CMIP6 (ISMP6)”
Isabel Nias: “Modeling the Greenland Ice Sheet’s Committed Contribution to Sea Level Rise During the 21st Century”
William Sweet: “2018/19 State of U.S. High-tide Flooding with a 2019/2020 Outlook”
Scott Andrew Kulp: “More Accurate Global Elevation Data Predicts a Far More Vulnerable Global Coastline”
Michael J. Willis: “Very High-resolution Topography of Coastal Megacities for Testing Inundation Scenarios”
Brett A. Buzzanga: “Towards a Cost-effective approach for Vertical Land Motion Mapping Integrating InSAR and GNSS: An Application in Hampton Roads, Virginia”
Yara Mohajerani: “Regional Atmospheric Climate Model Evaluation in Getz and Amery Ice Shelf Basins Using GRACE” (poster session)
David P. Bekaert: “Development of Open-access Standardized InSAR Displacement Products by the Advanced Rapid Imaging and Analysis (ARIA) Project for Natural Hazards”
Thomas Frederikse: “Combining Paleo Records, Tide Gauges, and Process Estimates to Constrain 20th Century Sea-level Rise in the South Atlantic Ocean”
Daniel Gilford: “Efficacy of Last Interglacial Estimates for Constraining Probabilistic Projections of Future Antarctic Sea Level Contributions”
Zoe Screwvala: “Modeling Future Mass Balance of Glaciers in Alaska Using Python Glacier Evolution Model” (poster session)
Eduard Roderik Heijkoop: “Comparison of Remote Sensing Techniques for Determining Mean Sea Level Near Coastal Megacities and its Impact on the Effects of Sea Level Change” (poster session)
Em Blackwell: “Flood Hazards Along the Coast of California Due to Vertical Land Motion and Sea-level Rise” (poster session)
Benjamin Strauss: “A Dynamic Global Sea-level Rise and Coastal Flood Risk Map”
Sonam Futi Sherpa: “An Unsupervised Probabilistic Method for Large-scale Flood Mapping: Exploring Full Archive of Sentinel-1A/B Satellites over India, and Iran”
Tessa Gorte: “How Well Do Climate Models Capture Antarctic Ice Sheet Surface Mass Balance over the 19th and 20th Centuries?”
Johan Nilsson: “Ice-sheet-wide Comparison of Coincident Laser and Radar Observations from ICESat-2 and CryoSat-2 for Greenland and Antarctica”
Carmen Boening: “Land/Ocean Water Exchange – Impacts on the Global Hydrologic and Sea-level Budget”
Benjamin Hamlington: “Extension of Satellite-measured Terrestrial Water Storage for Longer-term Water Cycle Studies”
Alex Gardner: “ICESat-2: Next Generation Estimates of Glacier Mass Change”
Hrishikesh Arvind Chandanpurkar: “Using a Climate-based Historical Reconstruction of GRACE Data to Separate Human- and Climate-driven Groundwater Trends”
Isabella Velicogna: “Continuity of Measurements of Time-variable Gravity Across the GRACE and GRACE-FO Missions over Greenland, Antarctica and the World’s Glaciers and Ice Caps.”
David Rounce: “The Impact of Debris Cover and Glacier Dynamics on Projections of Glacier Mass Change in High Mountain Asia” (poster session)
Enrico Ciraci: “Water Budget of the Indus River Basin between 2002 and 2015” (poster session)
Maria Zita Hakuba: “What Can Sea-level Change Tell Us About Earth’s Energy Imbalance?” (poster session)
Erik Ivins: “Toward a Baseline GIA Correction for Antarctica and Implications for East Antarctic Ice-mass Balance”
Emre Havazli: “Use of Geodetic Observations for Regional Monitoring of Vertical Land Motion Along Eastern Seaboard United States”
Jan Lenaerts: "Observing and Modeling Ice-sheet Surface Mass Balance"