Ocean physical-biogeochemical interactions in the CMIP6 and E3SM Earth System Models

Ocean physical-biogeochemical interactions in the CMIP6 and E3SM

Energy Exascale Earth System Model (E3SM)

The Energy Exascale Earth System Model (E3SM) project includes Earth System Models, simulations, and predictions to investigate energy-relevant science using code optimized for DOE's advanced supercomputers.

Source: NVCL Web Page Source

Earth System Models

Takamitsu Ito, Georgia Institute of Technology (Principal Investigator)

Annalisa Bracco, Georgia Institute of Technology (Co-principal Investigator)

Luke Van Roekel, Los Alamos National Laboratory (Unfunded Collaborator)

Yohei Takano, Los Alamos National Laboratory (Unfunded Collaborator)

The global carbon cycle

carbon cycle

The movement and exchange of carbon through living organisms, the ocean, the atmosphere, rocks and minerals, and other parts of the Earth.

Source: a student's guide to Global Climate Change Source

is integral to the Earth System. Its three major reservoirs

reservoir

A manmade lake that is created when a dam is built on a river. River water backs up behind the dam creating a reservoir.

Source: USGS Source

(land, atmosphere, and ocean) exchange carbon with the ocean containing the vast majority (> 90 %) of the carbon. In the past two centuries the anthropogenic tapping into fossil carbon in the geologic reservoir has dramatically altered the global carbon cycling. As a result, over time, the ocean has switched from being a small net source of carbon to the atmosphere to become a significant sink. The excess anthropogenic carbon that has been accumulating in the ocean is altering its chemistry and the marine ecosystems.

ecosystem

A natural community of plants, animals, and other living organisms and the physical environment in which they live and interact.

Source: A student's guide to Global Climate Change Source

At the same time, climate change

climate change

A change in the average conditions — such as temperature and rainfall — in a region over a long period of time.

Source: NASA Climate Kids Source

is modifying the ocean physics, with consequences for the transport of carbon into the ocean. Changing ocean circulation is similarly important for the global oxygen cycling. Approximately half of oxygen production occurs in the ocean, but changes in ocean transport, mixing and biological production are changing oxygen production and cycling. Earth System Models

earth system model (ESM)

A model that simulates how chemistry, biology, and physical forces work together. These models are similar to, but much more comprehensive than, global climate models.

Source: U.S. Department of Energy Source

(ESMs) are critical tools to explore these changes as they represent underlying physical and biochemical processes

biochemical process

The interaction of organisms with their abiotic (non-living part of an ecosystem) environment and other organisms by chemical means

Source: Ecological Biochemistry: Environmental and Interspecies Interactions Textbook Source

and their interactions in the context of changing global climate. Unfortunately, these models underestimate the amplitude of the changes in ocean carbon uptake and dissolved oxygen

dissolved oxygen

The amount of oxygen that is present in water. Water bodies receive oxygen from the atmosphere, runoff, and from aquatic plants.

Source: EPA Environmental Protection Agency Source

content on the timescales of tens of years. Additionally, they disagree over the sign of predicted changes in dissolved oxygen in the tropical oceans under global warming scenarios. These disagreements hinder the use of ESM-based predictions and limit their application to the study of ecosystem health and fisheries research. This project has three main objectives related to understanding of the processes and feedbacks regulating the ocean carbon and oxygen cycling and their representation in ESMs. The first objective is to evaluate the model’s ability of the U.S. Department of Energy (DOE) Energy Exascale Earth System Model (E3SM) to represent the interactions between physical and biogeochemical processes

biogeochemical processes

The complex interactions and transformations of chemical elements and compounds that occur throughout Earth's ecosystems, such as nutrient and element cycling between living organisms, the atmosphere, hydrosphere, lithosphere, and pedosphere (soil).

Source: Source

in the ocean. A growing amount of observational data now enables us to evaluate the model’s ability to represent the air-sea exchange of carbon dioxide

carbon dioxide (CO2)

An important heat-trapping gas, also known as a greenhouse gas, that comes from the extraction and burning of fossil fuels (such as coal, oil, and natural gas), from wildfires, and natural processes like volcanic eruptions.

Source: NASA Source

and dissolved oxygen contents on the timescale of years to decades. Furthermore, we will compare E3SM against other ESMs participating in the Couple Model Inter-comparison Project Phase 6 (CMIP6). The second objective is to characterize the patterns of physical and biogeochemical variability and their spatio-temporal linkages in the oceans. We will characterize key physical and biological processes and their sensitivities to modes of climate variability using both standard statistical analysis and complex network analysis tools. The third objective is to test several hypotheses behind the three key mechanisms that regulate the upper ocean carbon and oxygen cycling, namely, water mass distribution, ventilation, and biological production. We hypothesize that, together, these processes control mean state and changes in the oceanic inventories of carbon and oxygen, and explain the two major issues that are common among state-of-the-art ESMs around the world mentioned earlier. In summary, this project will improve scientific understanding of physical-biogeochemical interactions focusing on two key shortcomings of ESMs, and will deliver an analysis framework that can be applied to observational and model-derived physical and biogeochemical data. All analysis tools resulting from this project will be shared in the public domain.