Attributions of past regional sea level variations and projection of future sea level changes

Co-Is/Collaborators

Hrishikesh Chandanpurkar, Ian Fenty, Ichiro Fukumori, Thomas Frederikse, Alex Gardner, Patrick Heimbach, Dimitris Menemenlis, Fernando Paolo, Christopher Piecuch, Rui Ponte, John T. Reager, Ou Wang, Hong Zhang

Background

Significant knowledge gaps exist in the attributions of regional sterodynamic sea level (SL) variations in the past and the sources of uncertainties for regional sterodynamic SL projections. Recent advance of the Estimating the Circulation and Climate of the Ocean (ECCO) state estimation system, the associated sensitivity analysis tools, and the ongoing CMIP6 effort present a timely opportunity to narrow these knowledge gaps. The goal of this project is to improve the understanding of the forcing mechanisms for regional sterodynamic SL variations during the satellite altimeter era and for the projected SL changes in the 21st century. To accomplish the goal, we will perform investigations using a combination of ECCO global and regional high-resolution forward model sensitivity experiments, sensitivity analysis aided by the ECCO adjoint model, and projected forcings for the 21-century from CMIP6.

Expected Significance

Our proposed research is expected to narrow the knowledge gaps in regional sterodynamic SL attributions by elucidating the salient ocean dynamics in response to different forcings. The proposed effort will also improve the understanding of the effects of the 21st-century projected changes of these forcings and the inter-model discrepancies on regional steorodynamic SL projections. This will provide important feedback to the climate modeling community to improve regional SL projections. Our proposed effort will also (a) enhance the research in Sea Level Rise, a Science and Applications Priority Area described in the National Academies report for the Decadal Survey (cf. Table S.1), and (b) bolster the research on “Regional Sea-Level Change and Coastal Impacts”, a WCRP Grand Challenge.

Objectives

Objective 1: To decipher the relative contributions of atmospheric, hydrologic, and cryospheric forcings to regional sterodynamic SL variations from sub-seasonal to tri-decadal time scales during the altimeter era and to elucidate the salient ocean dynamic processes.
Objective 2: To estimate the contributions of the 21st-century projected changes in atmospheric, hydrologic, and cryospheric forcings to regional sterodynamic SL projections and to quantify the effects of forcing ensemble spreads on regional SL projection uncertainties.

Deliverables

Provide 21-century projections of regional sterodynamic SL for selected coastal locations.
Provide the adjoint sensitivities of SL to forcings, ensemble average for each forcing, and the scripts for regional sterodynamic SL projection to the Sea Level Change Science Team Web Portal (SLCST), which allows users to perform projection using an individual forcing or a combination of forcings, and to visualize the corresponding impacts on the projections.
Combine the projections with those for non-sterodynamic processes to be developed by other SLCST members to develop synthesized team products.