About

Sylvia Dee is an associate professor and climate scientist at Rice University, specializing in climate change and the past, present, and future of Earth’s hydrological cycle. She completed her undergraduate degree in Civil and Environmental Engineering with certificates in Geological Engineering and Environmental Sciences at Princeton University, and earned her Ph.D. at the University of Southern California Earth Sciences department. Her research focuses on how Earth’s modes of natural variability, such as El Niño and La Niña events, interact with climate change to influence weather and climate extremes, including flooding hazards on the Mississippi River. Her lab evaluates climate model data to understand future risks to human and natural systems. Sylvia Dee has held postdoctoral fellowships at the University of Texas Institute for Geophysics and Brown University. She was named a National Academies of Science and Engineering Gulf Research Program Early-Career Research Fellow in 2021 for her work on climate change impacts on the Gulf of Mexico. Outside of her research, she teaches courses in environment and society, introduction to climate change science, paleoclimate, and climate physics and modeling. She actively engages in environmental science programming for the Girl Scouts of the USA, for which she received the 'Global Leadership Award' by the Girl Scouts of New England. Additionally, she is a regular contributor to media coverage on climate change through outlets such as NPR, AccuWeather, and the Houston Chronicle. Sylvia Dee enjoys working with Rice undergraduates to find solutions to environmental problems.

Research topics

• Geology
• Computer Science
• Environmental science
• Oceanography
• Climatology
• Geography
• Meteorology
• Paleontology
• Database
• Atmospheric sciences
• Seismology

Selected publications

• CLUBB Reduces Low‐Cloud Dependency on Shallow Convective Mixing in the Community Atmosphere Model: Insight From Stable Water Isotopes

  Journal of Geophysical Research Atmospheres · 2025-07-01 · 2 citations

  articleOpen accessSenior author

  Abstract Modeling experiments and field campaigns have evaluated shallow convective mixing as a potential constraint on the low‐cloud climate feedback, which is critical for establishing climate sensitivity. Yet the apparent relationship between low‐cloud fraction and shallow convective mixing differs substantially among general circulation models (GCMs), large eddy simulations, and both remote sensing and in situ observations. Here, we consider how changes in GCMs' representations of subgrid‐scale vertical moist fluxes can alter the cloud‐mixing relationship. Using vertical profiles of water vapor isotope ratios ( δD ) to characterize the strength of shallow convective mixing in a manner that can be compared directly to satellite observations, we evaluate the cloud‐mixing relationship produced in tiered experiments with the Community Atmosphere Model (CAM). From versions 5 to 6 of CAM, the most notable physics change is CLUBB, a scheme that unifies the representation of shallow convection and boundary layer turbulence through a joint probability density function (PDF) for subgrid velocity and moisture. CLUBB reduces the covariance between low‐cloud fraction and shallow convective mixing, producing a bivariate distribution that is more similar in character to monthly averaged satellite observations. Using parameter sensitivity experiments, we argue that CLUBB's ability to simulate skewness in the distribution of vertical velocity produces more isolated but stronger moist updrafts, which reduce the grid‐mean low‐cloud fraction while maintaining efficient hydrological connectivity between the boundary layer and the free troposphere. These results suggest that mixing is not an effective predictor of low‐cloud feedback in GCMs with PDF closure schemes.

  PublisherDOI

• Water Isotope Model Intercomparison Project (WisoMIP): Present-day Climate

  2025-07-23

  preprintOpen access

  We present the first results of the Water Isotope Model Intercomparison Project (WisoMIP), with Phase 1 focused on modern simulations (1979–2023) from a suite of isotope-enabled atmospheric general circulation models nudged to ERA5 reanalyses. Water sources, mixing, and rainout history influence the isotopic composition of vapor and precipitation, making these simulations powerful tools for tracing the global water cycle. By prescribing identical winds, sea surface temperatures, and sea ice conditions, we isolate differences in water isotope behavior across models, controlling for variability in atmospheric dynamics and mean climate. Our analyses show that the ensemble mean best matches observations, as individual model errors cancel out to yield a more accurate representation of Earth’s isotope distributions. We also evaluate trends and responses to major climate modes during the recent warming period, highlighting regional and temporal sensitivities in the isotope signals. These diagnostics extend beyond traditional model evaluation metrics (e.g., temperature, precipitation) to reveal uncertainties in physical processes and guide improvements in model parameterizations. The resulting modern nudged ensemble dataset serves as a benchmark for isotope-enabled model development, satellite product comparison, and understanding of water cycle changes in a warming climate. Given its standardized design and broad participation, WisoMIP provides a valuable “isotope reanalysis’ product for applications ranging from paleoclimate reconstruction to model tuning. Our work demonstrates the importance of coordinated isotope model evaluation in advancing the use of water isotopes as a diagnostic tool in climate science.

  PublisherOA PDFDOI

• Impact of 21st century climate change on Mississippi River Basin discharge in CESM2 large ensemble projections

  Global and Planetary Change · 2025-02-15 · 6 citations

  articleOpen access

  The Mississippi River Basin (MRB), the fourth-largest river basin in the world, is an important corridor for hydroelectric power generation, agricultural and industrial production, riverine transportation, and ecosystem goods and services. Historically, flooding of the Mississippi River has resulted in significant economic losses. In a future with an intensified global hydrological cycle, the altered discharge of the river may jeopardize communities and infrastructure situated in the floodplain. This study utilizes output from the Community Earth System Model version 2 (CESM2) large ensemble simulations spanning 1930 to 2100 to quantify changes in future MRB discharge under a high greenhouse gas emissions scenario (SSP3–7.0). The simulations show that increasing precipitation trends exceed and dominate increased evapotranspiration (ET), driving an overall increase in total discharge in the Ohio and Lower Mississippi River basins. On a seasonal scale, reduced spring snowmelt is projected in the Ohio and Missouri River basins, leading to reduced spring runoff in those regions. However, decreased snowmelt and spring runoff is overshadowed by a larger increase in projected precipitation minus ET over the entire basin and leads to an increase in mean river discharge. This increase in discharge is linked to a relatively small increase in the magnitude of extreme floods (2 % and 3 % for 100-year and 1000-year floods, respectively) by the late 21st century relative to the late 20th century. Our analyses imply that under SSP3–7.0 forcing, the Mississippi River and Tributaries (MR&T) project design flood would not be exceeded at the 100-year return period. Our results harbor implications for water resources management including increased vulnerability of the Mississippi River given projected changes in climate. • Mississippi River discharge increases under the SSP3–7.0 emissions scenario. • Future precipitation increases outpace ET in Ohio and Lower Mississippi basins. • Reduced snowmelt in Missouri and Ohio basins is projected to lower spring discharge. • Discharge at Vicksburg is projected to rise, but Project Design Flood Level will not be exceeded at a 100-yr return period.

  PublisherDOI

• Evaluation of hydroclimatic biases in the Community Earth System Model (CESM1) within the Mississippi River basin

  Hydrology and earth system sciences · 2025-09-25 · 1 citations

  articleOpen accessCorresponding

  Abstract. The Mississippi River is a critical waterway in the United States, and hydrologic variability along its course represents a perennial consideration for trade, agriculture, industry, ecosystems, the economy, and communities. Simulations of past, historic, and projected river discharge have been widely used to assess the dynamics and causes of changes in the hydrology of the Mississippi River basin over long time scales and to put changes of climate in context. The Community Earth System Model version 1 (CESM1) offers such simulations to complement observational records of river discharge by providing fully coupled output from a state-of-the-art earth system model that includes a river transport model. Here, we compare observations and reanalysis datasets of key hydrologic variables to CESM1 output within the Mississippi River basin to evaluate model performance and bias. We show that the seasonality of simulated river discharge in CESM1 is shifted 3 months late relative to observations. This offset is attributed to seasonal biases in precipitation and runoff in the region. We also evaluate performance of several Coupled Model Intercomparison Phase 6 (CMIP6) models over the Mississippi River basin, and show that runoff in other models – notably the Community Earth System Model version 2 (CESM2) – more closely simulates the seasonal trends in the reanalysis data. Our results have implications for model selection when assessing hydroclimate variability on the Mississippi River basin, and show that the seasonal timing of runoff can vary widely between models. Our findings point to (1) a need for continued developments in the representation of land surface hydrology in earth system models for improvements in our ability to assess the causes and consequences of environmental change on terrestrial water resources and major river systems globally, and (2) a need for caution and understanding of biases when applying these tools to practical risk assessment.

  PublisherOA PDFDOI

• Leaf Wax Hydrogen Isotopes Reflect Storm Track Position Over Western North America

  Paleoceanography and Paleoclimatology · 2025-10-09

  preprintOpen access

  Abstract Proxy records of past climates have yielded powerful insights into regional hydroclimate dynamics. Novel insights may be gained by reconstructing spatiotemporal changes in precipitation isotopologues in past climate states that cannot be gleaned from individual site‐level studies. In this paper, we ask whether latitudinal gradients in the stable hydrogen isotopic composition of precipitation, as inferred from sedimentary leaf wax biomarkers, reflect aspects of large‐scale climate conditions in western North America (WNA). Modern coretop samples from offshore WNA show that leaf wax hydrogen isotopes broadly track the hydrogen isotopic composition of rainfall between 20 and 40N, but with an offset corresponding to a relatively constant “apparent fractionation” value. Poleward of 40N, the leaf wax signal may be complicated by fluvial transport of leaf waxes from the continental interior. Leaf wax‐inferred precipitation hydrogen isotopes show a shift to more negative values between 30 and 40N. We use modern observational data to show that this latitudinal range marks a major transition between the subtropical arid zone and the location of the midlatitude storm tracks over the northeast Pacific. Nudged water isotope‐enabled models capture the location of the arid to mesic climate transition with fidelity. This modern data set suggests that reconstructions of the latitudinal gradient of precipitation hydrogen isotopes can constrain the sensitivity of the storm tracks to shifts in climatic boundary conditions in past climate states. This approach can yield novel insights into past, present, and future hydroclimate variability in this arid region.

  PublisherOA PDFDOI

• Multi‐Centennial Spatial Coherency Among Atlantic Tropical Cyclones From Simulated and Reconstructed Storm Records

  Geophysical Research Letters · 2025-09-19 · 1 citations

  articleOpen access

  Abstract Proxy‐based reconstructions of long‐term Atlantic tropical cyclone (TC) variability reveal low‐frequency oscillations in regional TC landfalls over the Common Era. However, the limited spatial coverage and increased uncertainty of the proxy records complicates assessments of this feature. Here we present a new multi‐ensemble set of synthetic TCs downscaled from the Last Millennium Reanalysis project, which is based on sea surface temperatures that more accurately reflect past conditions. Throughout ensemble members, there are coherent multi‐centennial shifts in landfalls with persistent intervals of increased (decreased) occurrence along the eastern US concurrent with inverse activity in the southwest Caribbean and Gulf of Mexico, associated with basin‐scale redistributions of storm tracks. The emergent TC‐dipole from modeled climate provides context and support for its presence within proxy‐reconstructions. Furthermore, dipole recurrence across ensembles demonstrates that it arises from sea surface temperature‐informed climate processes. However, timing differences between ensembles indicate that transient atmospheric variability influences dipole position.

  PublisherDOI

• WISO-SAT: A global database of stable hydrogen isotopes in water vapor from eight satellite missions

  Research Square · 2025-10-21

  preprintOpen access
  PublisherOA PDFDOI

• Persisting Lakes on a Cold Mars: the Potential Role of Seasonal Ice Cover

  Abstracts with programs - Geological Society of America · 2025-01-01

  article
  PublisherDOI

• Seasonal Ice Cover Could Allow Liquid Lakes to Persist in a Cold Mars Paleoclimate

  AGU Advances · 2025-12-29

  articleOpen access

  Abstract Geomorphic and stratigraphic studies of Mars prove that extensive liquid water flowed and pooled on the surface early in Mars' history. Martian paleoclimate models, however, have difficulty simulating climate conditions warm enough to maintain liquid water on early Mars. Reconciling the geologic record and paleoclimatic simulations of Mars is critical to understanding Mars' early history, atmospheric conditions, and paleoclimate. This study uses an adapted lake energy balance model to investigate the connections between Martian geology and climate. The Lake Modeling on Mars for Atmospheric Reconstructions and Simulations (LakeM 2 ARS) model is modified from an Earth‐based lake model to function in Martian conditions. We use LakeM 2 ARS to investigate the conditions necessary to simulate a lake in Gale crater. Working at a localized scale, we combine climate input from the Mars Weather Research & Forecasting general circulation model with geologic constraints from Curiosity rover observations to identify potential climatic conditions required to maintain a seasonally ice‐free lake. Our results show that an initially small lake system (10 m deep) with ∼50 mm monthly water input and seasonal ice cover would retain seasonal liquid water for over 100 years, demonstrating conditions close to long‐term lake survivability. These results are an important step in resolving the historic disconnect between climate and geology on Mars. Continued use and iteration of LakeM 2 ARS will strengthen connections between Mars' paleoclimate and geology to inform climate models and enhance our understanding of conditions on early Mars.

  PublisherDOI

• Proxy System Biases partially resolve long-standing paleoclimate data-model discrepancies in Tropical East Africa

  Quaternary Science Reviews · 2025-07-04

  article
  PublisherDOI

Recent grants

• Collaborative Research: P2C2--Quantifying Holocene Climate Variations through Data Assimilation using Proxies and General Circulation Models (GCMs) Output

  NSF · $62k · 2019–2022

• Collaborative Research: P2C2--Variability, Impacts and Extremes of the ENSO-Asian Monsoon Relationship over the Common Era

  NSF · $325k · 2021–2024

• Collaborative Research: Evaluating the Past and Future of Mississippi River Hydroclimatology to Constrain Risk via Integrated Climate Modeling, Observations, and Reconstructions

  NSF · $472k · 2022–2025

• Collaborative Research: Constraining African Climate since the Last Glacial Maximum via integrated Climate and Proxy System Modeling

  NSF · $313k · 2019–2025

Frequent coauthors

• James M. Russell

  Brown University

  43 shared

• Nathan Steiger

  Columbia University

  34 shared

• Julien Emile‐Geay

  University of Southern California

  32 shared

• David Noone

  University of Auckland

  22 shared

• Jun Hu

  18 shared

• Carrie Morrill

  NOAA National Centers for Environmental Information

  17 shared

• Jesse Nusbaumer

  NSF National Center for Atmospheric Research

  16 shared

• Samuel E. Muñoz

  NOAA National Marine Fisheries Service Northeast Fisheries Science Center

  14 shared

Labs

• Sylvia Dee Climate LabPI

  Specializing in atmospheric modeling, water isotope physics, and paleoclimate data-model comparison.

Awards & honors

• National Academies of Science and Engineering Gulf Research…
• Global Leadership Award by the Girl Scouts of New England