About

Professor Tim DeVries leads the Ocean Circulation and Biogeochemistry lab, which focuses on understanding the physical, chemical, and biological processes that control the Earth's climate. His research emphasizes the exchange of heat and carbon between the ocean and atmosphere, key components in regulating global climate systems. Situated within the Atmospheric & Climate Science and Ocean Science domains, Professor DeVries' work contributes to advancing knowledge of ocean-atmosphere interactions and their impact on climate dynamics.

Research topics

• Environmental science
• Geology
• Oceanography
• Climatology
• Environmental chemistry
• Chemistry
• Biology
• Ecology
• Geography
• Paleontology
• Atmospheric sciences

Selected publications

• Potential conflicts between fishing and oceanic carbon sequestration in 15% of the ocean

  One Earth · 2025-03-27 · 2 citations

  articleOpen access
  PublisherOA PDFDOI

• High‐Frequency Correlations Between Winds and <i>p</i> CO ₂ Change the California Coastal Upwelling System From a CO ₂ Sink to a Source

  Geophysical Research Letters · 2025-07-14 · 4 citations

  articleOpen access

  Abstract Net sea‐air CO 2 flux can be calculated from observations of seawater and atmosphere partial pressure of CO 2 ( p CO 2 ) and estimates of the gas transfer velocity. Typically, these quantities are calculated at a monthly resolution, which misses potentially important high‐frequency temporal variability. Here, we calculated sea‐air CO 2 flux at a 3‐hourly resolution using a 10‐year mooring data set (2011–2020) from the central California coastal upwelling region. We identified a significant flux of CO 2 from the ocean to the atmosphere due to a positive correlation between seawater p CO 2 and wind speed at timescales of hours to days, particularly during the late spring and early summer upwelling season. Accounting for this variability changes the region from a net sink to a net source of CO 2 to the atmosphere. These findings imply that CO 2 fluxes computed from monthly‐resolution data may miss important shorter‐term variability that contributes to a net outgassing of CO 2 from the ocean.

  PublisherOA PDFDOI

• Synthesis of data products for ocean carbonate chemistry

  2025-05-15

  preprintOpen access

  Abstract. As the largest active carbon reservoir on Earth, the ocean is a cornerstone of the global carbon cycle, playing a pivotal role in modulating ocean health and regulating climate. Understanding these crucial roles requires access to a broad array of data products documenting the changing chemistry of the global ocean as a vast and interconnected system. This review article provides a comprehensive overview of 60 existing ocean carbonate chemistry data products, encompassing compilations of cruise datasets, derived gap-filled data products, model simulations, and compilations thereof. It is intended to help researchers identify and access data products that best align with their research objectives, thereby advancing our understanding of the ocean's evolving carbonate chemistry.

  PublisherDOI

• The combined impact of fisheries and climate change on future carbon sequestration by oceanic macrofauna

  Nature Communications · 2025-10-27 · 1 citations

  articleOpen access

  Although the role of marine macrofauna in the ocean carbon cycle is increasingly understood, the cumulative impacts of fisheries and climate change on this pathway remain overlooked. Here, using a marine ecosystem model, we estimate that each degree of warming reduces macrofauna biomass and carbon export by 4.2% and 2.46%, respectively. Under a high emission scenario (SSP 5–8.5), this translates to a 13.5% ± 6.6% decline in export by 2100, relative to the 1990s. Fishing further amplifies this reduction by up to 56.7% ± 16.3%, creating a sequestration deficit of 14.6 ± 10.3 GtC by 2100. On average, a 1% biomass loss from fishing results in a 0.8% decline in carbon export. However, sequestration durability (~600 years) remains unaffected. While measures restoring commercial macrofaunal biomass could yield carbon benefits comparable to mangrove restoration, multiple uncertainties limit their inclusion in the Nature-based Climate Solution portfolio, highlighting the need for further research. Marine animals play a key role in locking carbon deep in the ocean, slowing climate change. This study finds that fishing has already cut this service in half, with climate change expected to further reduce it in the future.

  PublisherOA PDFDOI

• The dominant sink of oceanic calcium carbonate occurs in undersaturated seawater

  Proceedings of the National Academy of Sciences · 2025-10-24 · 1 citations

  articleOpen access

  Calcium carbonate (CaCO 3 ) particles formed by marine organisms dissolve in seawater and on the ocean floor, constituting a key component of the global ocean carbon cycle. However, neither the magnitude nor the distribution of CaCO 3 dissolution in the modern oceans is well constrained. Here we diagnose CaCO 3 dissolution rates in major oceanic regions and reconstruct CaCO 3 settling flux using a data-constrained ocean circulation model and observational climatologies of global seawater alkalinity and dissolved oxygen. Our approach distinguishes the effects of ocean circulation and CaCO 3 dissolution on seawater alkalinity and dissolved oxygen, and involves only one free parameter, a restoring timescale, which is constrained by compiling carbonate export rates estimated in the literature. We find that CaCO 3 dissolution in shallow waters (above the saturation horizon of aragonite) is much smaller than some recent estimates. Excluding the upper 114 m of the euphotic zone, the fraction of CaCO 3 dissolution within aragonite saturated waters is only about 16.5 ± 5.5%. About 39.8 ± 4.5% of CaCO 3 dissolution occurs below the aragonite saturation horizon but above the saturation horizon of calcite. The remaining 43.7 ± 3.8% dissolves in the deep ocean in undersaturated seawater. These results suggest that the seawater CaCO 3 saturation state is the primary control on CaCO 3 dissolution in the ocean.

  PublisherDOI

• Testing Assumptions in the Modeling of Radiocarbon in Ocean Biogeochemical Models

  2025-11-14

  articleOpen access

  Radiocarbon (14C) is useful as an oceanic age tracer and constraint on air-sea gas exchange rates. Models that are used to interpret radiocarbon often make simplifying assumptions to reduce the complexity of the models. This study provides a quantitative assessment of four common assumptions in ocean radiocarbon models: neglecting biological fluxes, neglecting sources and sinks to due evaporation and precipitation (”virtual fluxes”), modeling the ratio of 14C to total carbon directly instead of separately as dual tracers, and assuming constant preindustrial atmospheric conditions. Using an ocean circulation model, we compared a control simulation consisting of an abiotic dual tracer model with no virtual fluxes and a constant preindustrial atmosphere to four other simulations, each testing the effects of these assumptions individually. We found the greatest discrepancy when spinning up the model under constant preindustrial atmospheric conditions as opposed to using historical reconstructions of CO2 and ∆14C values over the common era, with an error of about 5‰ at the surface and up to 15‰ in the oldest waters. Ignoring biological fluxes and modeling the ratio 14C/C as a tracer each induced a bias of less than 2‰ globally-averaged, which is no larger than measurement uncertainty and lower than previously estimated. No significant difference was found between model runs with or without virtual fluxes. We conclude that the common practices of simulating the 14C/C ratio and ignoring biological processes are suitable for accurate simulation of 14C, whereas assuming constant preindustrial atmospheric conditions may lead to the largest error.

  PublisherOA PDFDOI

• Deep Ocean Ventilation: A Comparison Between a General Circulation Model and Data‐Constrained Inverse Models

  Journal of Advances in Modeling Earth Systems · 2025-07-01 · 5 citations

  articleOpen access

  Abstract Ocean ventilation, or the transfer of tracers from the surface boundary layer into the ocean interior, is a critical process in biogeochemical cycles and the climate system. Here, we assess steady‐state ventilation patterns and timescales in three models of ocean transport: a 1 global configuration of the Nucleus for European Modeling of the Ocean (NEMO), a recent 2 solution of the Ocean Circulation Inverse Model (OCIM), and a 2 solution of the Total Matrix Intercomparison (TMI). We release artificial dyes in six surface regions of each model and compare equilibrium dye distributions as well as ideal age distributions. We find good qualitative agreement in large‐scale dye distributions across the three models. However, the distributions indicate that TMI and OCIM are more diffusive than NEMO. A shallow bias of North Atlantic ventilation in NEMO contributes to a stronger presence of the North Atlantic dye in the mid‐depth Southern Ocean and Pacific. This isopycnal communication between the North Atlantic surface and the mid‐depth Pacific is very slow, however, and NEMO simulates a maximum age in the North Pacific (NP) about 900 years higher than the data‐constrained models. Overly slow NP ventilation persists across NEMO sensitivity experiments encompassing our current best knowledge of diapycnal and isopycnal mixing, pointing to biases in subarctic Pacific dynamics. This study provides a synoptic picture of deep ocean ventilation and a framework for assessing its representation in general circulation models.

  PublisherDOI

• Corrigendum: Metrics for quantifying the efficiency of atmospheric CO₂ reduction by marine carbon dioxide removal (mCDR) (2024 <i>Environ. Res. Lett.</i> 19 104053)

  Environmental Research Letters · 2025-07-11

  erratumOpen access
  PublisherDOI

• Seasonality in Marine Organic Carbon Export and Sequestration Pathways

  2025-06-11

  preprintOpen access

  The ocean’s biological carbon pump transports organic carbon from the surface to depth via three main pathways: the gravitational sinking of particles, active transport by vertically migrating zooplankton, and mixing and advection of suspended and dissolved organic carbon. Here, we use a global data-assimilated ocean biogeochemical model to diagnose the seasonal variability of carbon export and sequestration by these gravitational, migrant, and mixing pumps. The total carbon export and sequestration are 9.8±0.8 PgC yr -1 and 1296±21 PgC, respectively, similar to previous estimates that do not consider seasonality. However, the seasonality of the export and sequestration pathways is highly variable. In subtropical regions the seasonal amplitude of carbon export is ~20-30% of the annual mean: gravitational and migrant pump export peak during winter, while mixing pump export peaks during spring and early summer. Contrastingly, in subpolar regions the seasonal amplitude of the pumps is ~40-60% of the annual mean: export and sequestration by the gravitational and migrant pumps peak in the summer, while the mixing pump strongly opposes this seasonality, reaching a maximum during the winter. The gravitational "e-ratio", or ratio of gravitational carbon export to net primary production, shows strong seasonal variability. The seasonal variability of the gravitational e-ratio is ~0.1 at high latitudes, with higher values in the summer compared to winter. Resolving seasonality reduces the inferred geographic variability of the e-ratio compared to annual-mean models, demonstrating the importance of seasonal observations and models to understand the processes regulating carbon export and sequestration.

  PublisherOA PDFDOI

• Toward the inclusion of oceanic conservation measures in the Nature-based Climate Solution portfolio

  2025-03-26

  preprintOpen access

  It is clear now that Nature-based Climate Solutions (NbCS) – solutions designed to protect, restore, and sustainably manage ecosystems to mitigate climate change – are needed to achieve the net-zero climate targets. In a context where NbCS over-rely on land ecosystems, it is necessary to seek natural analogs in the ocean by focusing on components that contribute to oceanic carbon sequestration and that we can target through conservation measures, such as fish and the seabed.Here, we estimate the past and future influence of fisheries on the carbon cycle by assessing their impact on the carbon sequestration potential of fish, as well as their contribution to greenhouse gas emissions, with the ultimate goal of discussing their potential inclusion in the NbCS portfolio.We show that before the development of the fishing industry, fish of commercial interest induced a carbon export flux of 0.22 GtC.yr-1 (eq. to 0.80 GtCO2.yr-1), and that exploitation has reduced export to 0.10 GtC.yr-1 (eq. to 0.36 GtCO2.yr-1). This means that the restoration of macrofauna populations towards their historical levels has a climate change mitigation potential of 0.124 GtC.yr-1 (eq. to 0.45 GtCO2.yr-1), an estimate of the same order of magnitude as the one of mangroves restoration measures. Yet, as the vast ocean also plays a pivotal role in addressing socio-economic goals such as fisheries or food security, protecting oceanic areas for climate action should not impede these socio-economic goals. Consequently, finding areas where these potential conflicts are minimized is necessary to better inform the spatial management of fisheries. Regarding epipelagic fisheries, we find that most of the opportunities to safeguard and increase fish carbon sequestration lie in the high seas. Regarding bottom-trawling fisheries, the Arctic Ocean emerged as an area of major interest. Indeed, in a context where the Arctic would be sea-ice-free by the 2030s, these new open areas where the sediment carbon is still intact would soon become new bottom-trawling fishing grounds. We show that avoiding the development of these fisheries will avoid the emission of greenhouse gas emissions from fossil fuel burning and seabed carbon disturbance, without imperilling existing bottom-trawling fisheries. Our results therefore suggest that oceanic conservation measures are options to be considered for expanding the NbCS portfolio.

  PublisherDOI

Recent grants

• Collaborative Research: What controls the marine refractory DOC reservoir?

  NSF · $390k · 2021–2027

• Using machine learning to quantify historical changes in ocean heat content

  NSF · $364k · 2020–2026

• Collaborative research: Combining models and observations to constrain the marine iron cycle

  NSF · $274k · 2017–2020

• Quantifying mechanisms of variability in ocean CO2 uptake 1980-present

  NSF · $364k · 2020–2026

Frequent coauthors

• François Primeau

  32 shared

• Mark Holzer

  UNSW Sydney

  22 shared

• Saeed Roshan

  University of California, Santa Barbara

  18 shared

• Aaron Bagnell

  University of California, Santa Barbara

  18 shared

• Paul Tréguer

  17 shared

• Judith Hauck

  16 shared

• Aude Leynaert

  Université de Bretagne Occidentale

  15 shared

• David A. Siegel

  15 shared

Labs

• Tim DeVries's LabPI

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Education

• Ph.D., Earth System Science

  University of California, Irvine