Deconto, Robert

Job Title

Professor, Department of Geosciences

Last Name

Deconto

First Name

Robert

Discipline

Earth Sciences

Expertise

climatology earth
paleoclimatology
system modeling

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Search Results

Now showing 1 - 6 of 6

Session A: Climate Change - Climate Change and Sea Level Rise, Lessons from the Past and Models of the Future
(2011-11-18) Deconto, Robert
Recent observations of the polar ice sheets show an accelerating rate of fresh water input to the global ocean, yet the dynamic behavior of the ice sheets and the potential rate and magnitude of future sea level rise remain difficult to predict. New geological discoveries from the Arctic and Antarctic indicate a highly sensitive polar climate system, and far greater variability of the ice sheets than previously suspected. Here, we’ll review some of these recent findings in the context of new climate and ice sheet modeling studies, providing a geological perspective on climate sensitivity and the potential response of the ice sheets to a warming world.
The Paris Climate Agreement and future sea level rise from Antarctica
(2021-01-01) DeConto, Robert M.; Pollard, David; Alley, Richard B.; Velicogna, Isabella; Gasson, Edward; Gomez, Natalya; Sadai, Shaina; Condron, Alan; Gilford, Daniel M.; Ashe, Erica L.; Kopp, Robert E.; Li, Dawei; Dutton, Andrea; Deconto, Robert; Deconto, Robert
Three dimensional ice sheet model output for select model simulations in netCDF format. Please click the blue download button to download 3deg.nc (18MB).
Impact of climate change on New York City’s coastal flood hazard: Increasing flood heights from the preindustrial to 2300 CE
(2017-01-01) Garner, Andra J.; Mann, Michael E.; Emanuel, Kerry A.; Kopp, Robert E.; Lin, Ning; Alley, Richard B.; Horton, Benjamin P.; Deconto, Robert M; Donnelly, Jeffrey P.; Pollard, David
The flood hazard in New York City depends on both storm surges and rising sea levels. We combine modeled storm surges with probabilistic sea-level rise projections to assess future coastal inundation in New York City from the preindustrial era through 2300 CE. The storm surges are derived from large sets of synthetic tropical cyclones, downscaled from RCP8.5 simulations from three CMIP5 models. The sea-level rise projections account for potential partial collapse of the Antarctic ice sheet in assessing future coastal inundation. CMIP5 models indicate that there will be minimal change in storm-surge heights from 2010 to 2100 or 2300, because the predicted strengthening of the strongest storms will be compensated by storm tracks moving offshore at the latitude of New York City. However, projected sea-level rise causes overall flood heights associated with tropical cyclones in New York City in coming centuries to increase greatly compared with preindustrial or modern flood heights. For the various sea-level rise scenarios we consider, the 1-in-500-y flood event increases from 3.4 m above mean tidal level during 1970–2005 to 4.0–5.1 m above mean tidal level by 2080–2100 and ranges from 5.0–15.4 m above mean tidal level by 2280–2300. Further, we find that the return period of a 2.25-m flood has decreased from ∼500 y before 1800 to ∼25 y during 1970–2005 and further decreases to ∼5 y by 2030–2045 in 95% of our simulations. The 2.25-m flood height is permanently exceeded by 2280–2300 for scenarios that include Antarctica’s potential partial collapse.
CO₂ and tectonic controls on Antarctic climate and ice-sheet evolution in the mid-Miocene
(2021-01-01) Halberstadt, Anna Ruth; Chorley, Hannah; Levy, Richard H.; Naish, Timothy; Deconto, Robert M.; Gasson, Edward; Kowalewski, Douglas E.
Antarctic ice sheet and climate evolution during the mid-Miocene has direct relevance for understanding ice sheet (in)stability and the long-term response to elevated atmospheric CO2 in the future. Geologic records reconstruct major fluctuations in the volume and extent of marine and terrestrial ice during the mid-Miocene, revealing a dynamic Antarctic ice-sheet response to past climatic variations. We use an ensemble of climate – ice sheet – vegetation model simulations spanning a range of CO2 concentrations, Transantarctic Mountain uplift scenarios, and glacial/interglacial climatic conditions to identify climate and ice-sheet conditions consistent with Antarctic mid-Miocene terrestrial and marine geological records. We explore climatic variability at both continental and regional scales, focusing specifically on Victoria Land and Wilkes Land Basin regions using a high-resolution nested climate model over these domains. We find that peak warmth during the Miocene Climate Optimum is characterized by a thick terrestrial ice sheet receded from the coastline under high CO2 concentrations. During the Middle Miocene Climate Transition, CO2 episodically dropped below a threshold value for marine-based ice expansion. Comparison of model results with geologic data support ongoing Transantarctic Mountain uplift throughout the mid-Miocene. Modeled ice sheet dynamics over the Wilkes Land Basin were highly sensitive to CO2 concentrations. This work provides a continental-wide context for localized geologic paleoclimate and vegetation records, integrating multiple datasets to reconstruct snapshots of ice sheet and climatic conditions during a pivotal period in Earth's history.
Improvements in one-dimensional grounding-line parameterizations in an ice-sheet model with lateral variations (PSUICE3D v2.1)
(2020-01-01) Pollard, David; DeConto, Robert M
The use of a boundary-layer parameterization of buttressing and ice flux across grounding lines in a two-dimensional ice-sheet model is improved by allowing general orientations of the grounding line. This and another modification to the model's grounding-line parameterization are assessed in three settings: rectangular fjord-like domains – the third Marine Ice Sheet Model Intercomparison Project (MISMIP+) and Marine Ice Sheet Model Intercomparison Project for plan view models (MISMIP3d) – and future simulations of West Antarctic ice retreat under Representative Concentration Pathway (RCP)8.5-based climates. The new modifications are found to have significant effects on the fjord-like results, which are now within the envelopes of other models in the MISMIP+ and MISMIP3d intercomparisons. In contrast, the modifications have little effect on West Antarctic retreat, presumably because dynamics in the wider major Antarctic basins are adequately represented by the model's previous simpler one-dimensional formulation. As future grounding lines retreat across very deep bedrock topography in the West Antarctic simulations, buttressing is weak and deviatoric stress measures exceed the ice yield stress, implying that structural failure at these grounding lines would occur. We suggest that these grounding-line quantities should be examined in similar projections by other ice models to better assess the potential for future structural failure.
Could the Last Interglacial Constrain Projections of Future Antartic Ice Mass Loss and Sea-Level Rise?
(2020-01-01) Gilford, Daniel M.; Ashe, Erica L.; Deconto, Robert M.; Kopp, Robert E.; Pollard, David; Rovere, Alessio
Previous studies have interpreted Last Interglacial (LIG; ∼129–116 ka) sea‐level estimates in multiple different ways to calibrate projections of future Antarctic ice‐sheet (AIS) mass loss and associated sea‐level rise. This study systematically explores the extent to which LIG constraints could inform future Antarctic contributions to sea‐level rise. We develop a Gaussian process emulator of an ice‐sheet model to produce continuous probabilistic projections of Antarctic sea‐level contributions over the LIG and a future high‐emissions scenario. We use a Bayesian approach conditioning emulator projections on a set of LIG constraints to find associated likelihoods of model parameterizations. LIG estimates inform both the probability of past and future ice‐sheet instabilities and projections of future sea‐level rise through 2150. Although best‐available LIG estimates do not meaningfully constrain Antarctic mass loss projections or physical processes until 2060, they become increasingly informative over the next 130 years. Uncertainties of up to 50 cm remain in future projections even if LIG Antarctic mass loss is precisely known (±5 cm), indicating that there is a limit to how informative the LIG could be for ice‐sheet model future projections. The efficacy of LIG constraints on Antarctic mass loss also depends on assumptions about the Greenland ice sheet and LIG sea‐level chronology. However, improved field measurements and understanding of LIG sea levels still have potential to improve future sea‐level projections, highlighting the importance of continued observational efforts.