LuAnne Thompson - US grants

The role that eddies and Rossby waves generated by instabilities of the wind-driven circulation have in forcing the deep western boundary currents and the abyssal circulation will be studied using a combination of analytical and numerical models with increasing complexity. Of particular interest are the effects of the continental rise on eddy-driven circulation beneath the Gulf Stream and the weakly non-linear wave-mean flow interactions between a bottom trapped current and topographic Rossby waves.

94598356 Thompson This NYI award is to support LuAnne Thompson to undertake various process studies of isolated dynamical features (fronts and deep western boundary currents), the kinematics and dynamics of the western equatorial Atlantic and interannual variability in the tropical ocean circulation. Many of her new research areas are more physically oriented than theoretical. She has demonstrated her ability as a teacher by receiving a Danforth Distinction for Teaching award while she was at MIT. She also taught seminars as a post-doctoral fellow, and she has clearly defined her teaching plan for the University of Washington.

9818920
Thompson
The project is for a study of ocean dynamics and thermodynamics along the boundaries of the subtropical gyre in the North Pacific. The observed variability in surface height and temperature will be compared with numerical runs using Princeton isopycnal model. Along the northern boundary, the hypothesis is that this is where the mode waters are formed, which can carry information from atmospheric forcing into the ocean interior. An isopycnal model with an embedded bulk-mixed-layer will be used to investigate where in the water column heat content changes and whether these changes could affect SST at a later time. At the southern boundary of the gyre, the numerical model will be used to investigate whether this response is due to the interaction of the shoaling thermocline with buoyancy forcing in the mixed layer. The objective is to improve both model performance and interpretation of surface observations. After confirming model accuracy with observations, the model will be used to extend the analysis to longer time scales than are available from satellite measurements.

ABSTRACT

OCE-0095106

In this project, investigators at the University of Washington will quantify the physical mechanisms controlling the rates of biological carbon export and the uptake of anthropogenic carbon dioxide (CO2) in the North Pacific Ocean using a basin-wide general circulation model (GCM). The proposed model is operational and has already been used to evaluate mechanisms of subduction and water mass formation in the North Pacific and is currently being tested using chlorofluorocarbon tracers (CFCs).

The approach will be first to incorporate bomb-produced 14C into the model to validate its advective and diffusive fields. By adding this carbon-based tracer the model will then have been verified with both CFCs and 14C -- two tracers with different boundary conditions and time histories. Next, the three-dimensional distribution of biological carbon export and remineralization rates will be determined by using the observed distributions of several biological productivity tracers, specifically nitrate and phosphate (and their dissolved organic counterparts DON and DOP), three dissolved atmospheric gases (oxygen, argon, and nitrogen), and the 13C/12C ratio of the dissolved inorganic carbon (DIC). The PIs would then simulate the anthropogenic CO2 perturbation and utilize independent reconstructions of the anthropogenic DIC and 13C/12C changes in the North Pacific to validate model predictions. Finally, the model response to decadal variability in forcing would be examined.

There are several important reasons to choose the North Pacific Ocean as the site for a basin-scale modeling study. There are three JGOFS time-series sites that yield observed carbon fluxes and anthropogenic CO2 signals to compare to model predictions. The lack of deep-water formation at its poleward boundary simplifies the meridional circulation compared to the North Atlantic and southern oceans and justifies shorter model runs. Finally, the North Pacific has been the site of intensive chemical tracer measurements, specifically CFCs, 14C and 13C/12C, over the last 10 years.

The investigators will focus their modeling efforts on quantifying physical processes that likely control tracer, nutrient and CO2 fluxes in the upper ocean: 1) equatorial-subtropical and subtropical-subpolar exchange, 2) thermocline ventilation and isopycnal transport both with and without eddies, and 3) diapycnal mixing and the influence of eddies in the upper thermocline, and 4) the impact of decadal variability on biological carbon export.

0451479
Intellectual Merit: Tremendous advances in coupled climate models have been made in the last 10 years and they are being used both for both region and global predictions of climate. As such, there is an urgent need to evaluate their performance critically. The Community Climate System Model (CCSM version 2) developed at National Center for Atmospheric Research (NCAR) with help from the scientific community shows significant errors in sea surface salinity in the sub-polar North Pacific where the sea surface salinity (SSS) is too high. Preliminary investigation indicates that similar errors occur in the most recent version of the model. Related to the SSS errors are far too deep mixed-layers is the western sub-polar North Pacific. This project will analyze the fully coupled ocean-atmosphere model and a mixed-layer ocean coupled to an atmospheric general circulation model when it becomes available. In particular, the research will focus on what is causing the errors and what the consequences for the errors on the ocean model.
The expected results include a better understanding of the role that SSS plays in the coupled climate system. How errors in the upper ocean salinity budget act to break the fresh water dominated stratification in the subpolar North Pacific will be established. The importance of evaporation, precipitation, and runoff errors, as well as errors owing to sea-ice and ocean transport and mixing processes will be addressed. Tthe heat and fresh water transport in the ocean, with focus on the North Pacific and how mode and intermediate water form in the coupled model will also be examined. This study will lead to improved understanding on how the CCSM model works and what improvements need to be made in the model.
Broader Impacts: The proposed research will add a significant contribution to the evaluation and development of the Community Climate System Modeling (CCSM) effort at NCAR by members of the academic oceanographic community. The lead investigator is also a participant in a community effort to establish petascale computing needs for the geosciences. Direct involvement with the CCSM model will help in this effort. Both PI's are from an under-represented group in oceanography and the collaboration with CCSM scientists at NCAR will enable them to further develop their careers. The lead PI is also actively involved in the planning of a workshop to establish a mentoring network for women in physical oceanography.

0525874

Intellectual Merit
Recent observations of dissolved oxygen during repeat occupations of hydrographic sections have found increased apparent oxygen utilization within the thermocline of the South Indian, South Pacific, and south of Australia. The goal of this proposed research is to identify the role of variability in the physical processes or biological processes which result in changes in dissolved oxygen within the Southern Ocean thermocline, including Subantarctic Mode and Antarctic Intermediate Waters. Data analysis of the World Ocean Circulation Experiment (WOCE) and CLImate VARiability and predictability (CLIVAR) Repeat Hydrography Programs will be combined with model simulations with variable physical forcing using the Hallberg Isopycnal Model. Chlorofluorocarbons (CFCs) will be included in these studies. Where CFC measurements are available during repeat measurements, increases in the pCFC ages are co-located with the decreases in oxygen within the thermocline. Since CFCs are not affected by variability in biological processes, their distributions imply that variability in the physical forcing has produced the increased apparent oxygen utilization. The modeling study will confirm whether this is true as well in the southern ocean and will be used to determine the relative importance of the variability in physical forcing due to variability in the winds, surface buoyancy forcing, and gas exchange on the ventilation and circulation of the thermocline and mode waters of the Southern Ocean. Similar studies of the North Pacific have shown that the same model reproduces the observed decreases of oxygen in the deep thermocline from the 1980s to the 1990s. Because of the fidelity of the model, the basin wide results can be used to provide a context for the observed changes. In that work, changes in ventilation have been shown to be important near the formation region of the water mass in question, while circulation changes were more important further downstream.

Broader Impacts of Proposed Work
The results from this project will contribute to the interpretation of the carbon dioxide system measurements during the CLIVAR Repeat Hydrography. The fractional carbon method for determination of the anthropogenic carbon dioxide concentration relies on the assumption of steady state circulation, and then corrects for remineralization using Apparent Oxygen Utilization (AOU) and for air-sea disequilibrium using pCFC ages. It is clear that variability in physical forcing needs to be considered in the calculation of carbon uptake. The close collaboration of a CFC chemist and a physical oceanographer should provide new insight into this important problem. In addition, collaborations with the modeling group at GFDL will be continued to ground their modeling effort in interpretation of observations. The project will also contribute to the development of the biogeochemical component of the Hallberg Isopycncal Model and will make the offline tracer advection code available to the community in collaboration with GFDL. Two post-doctoral fellows and a graduate student will receive training in this interdisciplinary research project. The co-PI will continue to be involved in supporting women in physical oceanography through an effort supported by NSF and ONR to developing a mentoring network for junior women in the field.

0526011

The Okhotsk Sea plays an important role in the North Pacific Ocean circulation through its influence on the formation of the North Pacific Intermediate Water (NPIW). In addition, it has a highly variable sea ice cover, which influences not only water mass formation, but also the atmospheric circulation over the sub-polar North Pacific. The dense water formed along the Okhotsk Sea shelves is the source of this NPIW and depends critically on the details of the coastal polynyas and tidal mixing, and their relation to the stratification and mean circulation. Though recent observations have shown that brine rejection from sea ice sinks at the tidal front over the shelves, many questions remain as to the relationship among polynya openings, ice production, ocean-ice heat exchange, and shelf dynamics.

Intellectual merit:
In this project, oceanographers at the University of Washington will perform a series of sensitivity experiments with a regional coupled ice-ocean model to investigate the sea ice and water mass formation and their inter-annual variability. In addition to coupling the Regional Ocean Model System, a terrain following coastal ocean model, and the Community Sea Ice Model, a sophisticated dynamic-thermodynamic sea ice model, the researcher will also employ new, high quality datasets for model forcing, initialization, and verification. The outcomes of the work will include an integration of available data with a model of the Okhotsk Sea that will also take into account the important physical oceanographic processes in the region. An analysis of the heat and fresh water budgets of the region will also be made, focusing on both the seasonal cycle and inter-annual variability. The dense water formation in the model will be quantified, and the sensitivity of the model to the influence of tides will be tested. In addition to the regional modeling, the researcher will also analyze the influence of the Okhotsk Sea on a larger scale using the Community Climate System Model (CCSM, a global climate model). The regional ocean-ice model will be used to estimate the importance of processes that are absent from the CCSM.

Broader Impacts:
The results from this work will not only lead to an improved understanding of polynyas but also to the potential global importance of the Okhotsk Sea. In addition to training a graduate student, the work will also develop a partnership with the Community Climate System Model project at NCAR. The use of the CCSM sea-ice model in a regional context will help with future development of the CCSM as the new generation of super-computers allow for higher resolution climate simulations.

In this research project, investigators at the University of Washington will study the sensitivity of the North Pacific carbon cycle to changes in physical atmospheric forcing over the past few decades. Decade-scale changes in the North Pacific carbon cycle and related processes have been well documented through direct observations. Basic questions remain, however, about the controlling mechanisms, and little is known about the relationship between surface and thermocline variability. The investigators are motivated by a series of recent indications from both models and observations that fresh water forcing due to changes in the hydrological cycle plays an important role in the decadal variability of tracers of carbon cycle processes in both surface and thermocline waters. This issue can now be addressed using newly published historical ocean salinity trends. In addition, valuable data emerging from the CLIVAR program allows the relationships between changes in biogeochemical variability in surface waters and in the ocean interior to be explored.

The research plan will involve hind cast simulations with an ocean circulation/biogeochemical model to examine the sensitivity of surface carbon cycle parameters and interior distributions of O2 and DIC to changes in sea surface salinity as well as nutrients. The investigators have previously developed a model for investigations of physical-biogeochemical variability in the North Pacific basin. While the model currently has no carbon cycle, it does have biogeochemical cycles of nutrients and oxygen that are able to reproduce the climatological O2 and nutrient distributions, as well as the overall pattern of thermocline O2 changes observed during the late 20th century. The straightforward addition of a carbon cycle to the model therefore builds on a demonstrated capacity to capture important modes of physical and biogeochemical variability.

The results of these sensitivity experiments will then be assessed through a detailed comparison of model output to observed carbon cycle variability in the North Pacific based on ocean time series stations, together with data from the CLIVAR/CO2 Repeat Hydrography Program. This effort will take advantage of established collaborations with leading experimental carbon cycle scientists at the Pacific Marine Environmental Laboratory. Finally, the research team will conduct a series of attribution experiments to isolate and characterize the contribution of physical, biological and chemical processes to simulated carbon variability.

Although the study itself will be regionally specific, the study should have broader impacts for the study of the global ocean carbon cycle and related phenomena. The emphasis on the spatial signatures and relative importance of different processes controlling ocean carbon cycle variability should inform the community-wide understanding of the variability of the global carbon cycle. The project will support a young postdoctoral investigator and a beginning graduate student.

Numerous models have explored the impact of North Atlantic freshwater flood events in the context of abrupt climate change at the end of the last ice age, suggesting these events had major impact on the meridional overturning circulation (MOC) system. During the early deglaciation (roughly 16,600 to 13,000 BC), cataclysmic floods from proglacial Lake Missoula inundated eastern Washington-Oregon and passed into the Pacific Ocean via the Cascadia Basin. While we know that turbidity currents originating from these floods penetrated nearly 1000 km into the North Pacific to depths over 3km there is little understanding of the impact of this freshwater discharge on ocean circulation or climate. Unlike the North Atlantic, the most likely scenario for climate impact from freshwater discharge into the Northeast Pacific involves changes in structure of the upper ocean and thermocline properties.

This project will conduct modeling experiments (idealized ocean-only and fully-coupled numerical CCSM3 model simulations) to explore the impacts of a surface layer discharge event versus convection from a hyperpycnal, subsurface flow to test the hypothesis that flood induced changes in N. Pacific subploar-subtropical ocean circulation could influence the position of the intertropical convergence zone (ITCZ), thereby providing a mechanism for influencing climate via tropical air-sea interaction. The project will also use radiocarbon date core material to establish a chronology of outburst events.

Broader Impacts of Proposed Work

This project will enhance collaborations between physical oceanographers, paleoceanographers and paleoclimatologists. The Pacific Northwest Pleistocene floods are a phenomenon of great interest to the general public because they dramatically affected much of the regional landscape. Results of the proposed research will be used to educate the public about processes of current day climate change through connections to changes seen during glacial times. A young female post-doc will receive valuable cross-disciplinary training from three leading scientists in the geosciences.

Over the past two decades, several large observational climate programs in the Indian Ocean have collected a comprehensive chemical and physical oceanographic data set. In this project, all available Indian Ocean data will combined to investigate carbon cycling and decadal variability in the Indian Ocean. The timing of the project is such that the proposed work will supplement an ongoing NSF-funded project designed to determine the three-dimensional Indian Ocean circulation from hydrographic observations.

This project has two main goals: To perform a comprehensive, basin-wide study to determine the strength of the biological carbon pump in the Indian Ocean, and to investigate changes in ventilation time scales at the southern entry point to the Indian Ocean along 32°S. The proposed research effort consists of an extensive analysis of ventilation ages derived from analysis of transit time distributions (TTDs) and the corresponding mean ages. This age information will be used to estimate subsurface rates of oxygen utilization, denitrification, and calcium carbonate dissolution, and the amount of organic and inorganic carbon export from the surface ocean needed to support these rates. In addition, at 32°S, a time series of ventilation ages will be constructed based on four occupations of this section. This will provide time scales for the ventilation variability that can be seen in other properties and that may be related to the Southern Annual Mode (SAM). Correlations with meridional transport variations inferred from the three-dimensional Indian Ocean circulation estimates will also be examined.

The data analysis will be complemented by offline numerical simulations with an isopycnal ocean circulation model that includes tracers and basic biogeochemistry. In addition to sensitivity studies regarding the data methods used, a tracer adjoint for the offline code will be developed. With the adjoint, it will be possible to determine whether the source region of waters in the thermocline at 32°S changes during different states of the SAM and how changes in remote forcing may contribute to tracer age variability observed at 32°S.

Intellectual Merit: Inferring surface ocean carbon export rates from subsurface tracer data is an entirely data-based, "bottom-up approach" that provides estimates on a large scale. A novel tracer, sulfur hexafluoride, will be used in a dual tracer approach with chlorofluorocarbons to constrain transit time distributions and mean ventilation ages. The tracer adjoint model provides a tool to run tracers "backwards" to trace anomalies back to their surface origin.

Broader Impacts: The proposed work will contribute to the analyses of data from the CLIVAR/Carbon Repeat Hydrography Program and the study of decadal climate variability. The work is interdisciplinary, involving ocean physics and biogeochemistry, and will contribute to the study of the global carbon cycle. Studies of the Indian Ocean are timely because of the development of the Indian Ocean Global Ocean Observing System. All three investigators are involved in outreach activities at all educational levels from high school through mentoring women at the early states of their careers. A graduate student will be involved in the proposed work and receive training in ocean modeling and analyses of transient tracer data.

This project is a contribution to the U.S. CLIVAR (CLImate VARiability and predictability) Program.

This award will partially support the 6th Graduate Climate Conference at the University of Washington from October 26-28, 2012. Specifically, the award will be used to support the travel, meals and lodging costs for 30 US graduate students to participate in the conference.

The Graduate Climate Conference is an annual event that provides students with a discussion forum on all topics of climate change research - including atmospheric, biological, earth and ocean sciences - and allows the students to see how their own research fits into this breadth of climate research activities. The workshop provides a relaxed environment for interactions with individuals at a similar early career stage and the opportunity to develop a network of collaborative, interdisciplinary relationships that will prove beneficial throughout their careers.

This award provides support to the 8th annual Graduate Climate Conference, to be held at the University of Washington's Pack Forest Conference Center, Octoberst 31 to November 2nd 2014. The goal of the GCC is to provide a discussion forum for graduate students undertaking research on climate processes over an array of disciplines, including atmospheric, biological, earth, and ocean sciences, as well as human dimensions of climate variability and climate change. This is a unique setting, bringing together graduate students in a environment organized exclusively by graduate students to discuss current research in climate science. The collegial, single-session format is designed to expose graduate students studying a single aspect of the climate system to the research that other graduates are doing in all aspects of the climate system. This opportunity allows graduate students to familiarize themselves with the breadth of climate science as well as the enormous range of tools available to help answer complex questions. Through this interdisciplinary conference, we aim to better prepare graduate students for scientific inquiry in a world that increasingly demands interdisciplinary approaches. Approximately 90 graduate students selected through a competitive process will attend the GCC. NSF funds will be used to provide travel and subsistence for 40 students from US institutions.

This award provides support to the 10th annual Graduate Climate Conference (GCC), to be held at the University of Washington's Pack Forest Conference Center, October 28-30, 2016. The goal of the GCC is to provide a discussion forum for graduate students undertaking research on climate processes over an array of disciplines, with topics including atmosphere/ocean dynamics, biogeochemical cycles, clouds and aerosols, cryosphere processes, climate feedbacks, paleoclimate, regional climate, climate impacts, science-based climate policy, and human impacts. This is a unique setting, bringing together graduate students in a environment organized exclusively by graduate students to discuss current research in climate science. The collegial, single-session format is designed to expose graduate students studying a single aspect of the climate system to the research that other graduates are doing in all aspects of the climate system. The meeting allows graduate students to familiarize themselves with the breadth of climate science as well as the enormous range of tools available to help answer complex questions. The goal is to better prepare graduate students for scientific inquiry in a world that increasingly demands interdisciplinary approaches. Approximately 90 graduate students selected through a competitive process will attend the GCC. NSF funds will be used to provide travel and subsistence for 40 students from US institutions.

Marine heatwaves (MHWs) are devastating periods of extreme sea surface temperatures (SST) that disrupt marine ecosystems and the fishing industries that rely on them. Their effects include increased economic tension between nations and an unprecedented harmful algal bloom that threatened public health. These events have been observed throughout the global ocean, with several large scale persistent events occurring in the mid-latitudes over the last decade. Climate model simulations suggest that under continued global warming we can expect MHWs to become longer lasting, more frequent and intense, pushing ecological systems beyond their thermal coping limit, leading to irreversible impacts to the environment. While the satellite record of SST over the last 40 years allows characterization of past MHWs, the number of these devastating midlatitude events is limited, making it difficult to assess how unusual the events are. Event based analysis of the causes and consequences of individual events has given insight into important processes that control these particular events, but whether these processes remain important in the future is unclear. This research will make use of an extensive set of existing model simulations, including both different model configurations and ensembles or multiple realizations of similar runs for better statistical convergence. The analysis will yield insights into both the fidelity of the simulations in critical parts of the ocean and the predictability of heat waves. The impacts of MHWs are profound to both human and natural systems, and quantifying both the impact of climate change on their properties as well as an examination of the predictability of these events will ultimately help to mitigate and prepare for potential impacts in the future. Two graduate students will be trained to use the National Center for Atmospheric Research (NCAR) analysis tools, as well as work with NCAR scientists in developing new tools in Python for use in future analyses of extreme ocean events. The research team will also work with the Northwest Association of the Networked Ocean Observing Systems (NANOOS), hosted at the University of Washington, and the North Carolina Nature Conservancy office to write short articles about the results of this research. Results of this research will also be incorporated into undergraduate courses in coastal oceanography and climate at the University of Washington and the University of Wisconsin.

This project will take advantage of a suite of model simulations performed using the CESM (Community Earth System Model) including forced and coupled simulations at both low and high resolutions. An assessment of statistics of MHWs will be performed using a 40-member large ensemble of the climate from 1920 to 2100 allowing statistical robustness of event characteristics. Additional analysis of high resolution forced and coupled simulations will allow assessment of the fidelity of the representation of MHWs in boundary current regions where large biases are known to exist in low resolution simulation. In addition, a decadal prediction system using the same model version as the large ensemble will allow exploration of the role of ocean initialization in the predictability of these dangerous events. Typical analysis of MHW properties has used pointwise metrics, or metrics defined as area averages over fixed boxes. New integrated metrics for MHW characterization will be created that allow for MHWs that change shape and position over time, and will take into account heat stored below the surface. The role of climate variability in controlling MHWs will be assessed using the large ensemble, while comparison of high and low resolution models will allow for assessment of the robustness of the results from low resolution models. The focus on midlatitude events will include assessment of how ocean heat storage and re-emergence affect properties of MHWs.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).

The number of jobs that require Geoscience training continues to grow, but the number of students pursuing an education in this field is declining. In all science disciplines, the participation of individuals from historically marginalized groups does not match the proportion of the U.S. population as a whole, but their representation in the Geoscience workforce lags even further behind. At the same time, the impact of environmental challenges is greater and more severe for historically marginalized communities. Increasing the representation of these communities in the Geosciences is therefore fundamental to developing equitable solutions to these issues. Here, the PIs aim to pilot and test the effectiveness of a place- and issue-based recruitment and summer education program that is designed to increase community college student interest in, and retention in, the Geosciences as practiced at a research intensive university. In doing so, the PIs aim to develop educational approaches that can be adapted to any location, thereby supporting NSF goals of promoting the progress of Geosciences by increasing participation by all affected communities. In the long term, PIs also aim to advance NSF’s goals of improving the health and welfare of the communities most impacted by environmental challenges.

The project aims to test whether delivering fundamental, disciplinary content within a context that is meaningful to students can promote recruitment and retention of two-year college transfer students into the Geosciences, and particularly from local communities that may be economically challenged, underserved, and underrepresented in STEM. Researchers and educators in the University of Washington College of the Environment address both discovery and solutions-based science that bring together knowledge of the environment (Oceanography, Atmospheric Sciences, Earth Sciences) with the study of living marine resources, habitats and human communities. Using this expertise, PIs will develop a summer bridge program, conducted on a research vessel and at the institution's marine field station. The program will provide immersive experiential learning activities that explicitly link quantitative skill enhancement with Marine Geoscience via a deep, data-driven exploration of particular issues of community and political concern in the Pacific Northwest. Subsequently, students will engage in a series of cohort-building activities designed to facilitate community building during their first year with an eye towards enhancing student preparedness for advanced coursework in the Geosciences and to improve social learning.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.