| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
|
| Initial Amendment Date: | September 14, 2016 |
| Latest Amendment Date: | September 14, 2016 |
| Award Number: | 1634719 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Candace Major
OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
| Start Date: | September 15, 2016 |
| End Date: | August 31, 2020 (Estimated) |
| Total Intended Award Amount: | $497,913.00 |
| Total Awarded Amount to Date: | $497,913.00 |
| Funds Obligated to Date: |
|
| History of Investigator: |
|
| Recipient Sponsored Research Office: |
1500 SW JEFFERSON AVE CORVALLIS OR US 97331-8655 (541)737-4933 |
| Sponsor Congressional District: |
|
| Primary Place of Performance: |
308 Kerr Administration Building Corvallis OR US 97331-2140 |
| Primary Place of
Performance Congressional District: |
|
| Unique Entity Identifier (UEI): |
|
| Parent UEI: |
|
| NSF Program(s): | Marine Geology and Geophysics |
| Primary Program Source: |
|
| Program Reference Code(s): |
|
| Program Element Code(s): |
|
| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
An important unanswered question in climate science is what caused the increase of atmospheric carbon dioxide (CO2) concentrations during the last deglaciation. During the height of the last ice age, 20,000 years ago, climate was cold and CO2 concentrations were low, around 180 parts per million (ppm). Subsequently CO2 concentrations rose to about 280 ppm causing the climate to warm, ice sheets to melt and sea levels to rise. The last deglaciation was the last time in Earth's history when global climate warmed substantially, comparable to the warming projected for the coming centuries. Currently interactions between climate and the carbon cycle are not well understood, with possible implications for the accuracy of future climate projections.
This project it will contribute to a better understanding of Earth's coupled climate-carbon cycle system. Previous research suggests that the carbon that was missing in the atmosphere during the ice age may have been stored somewhere in the ocean, but at present it is not clear where it was, how it got there, or what mechanisms may have controlled its outgassing from the ocean to the atmosphere during the deglaciation. This project will synthesize carbon isotope data from ocean sediments and combine them with detailed model simulations in order to better understand the ocean's circulation and carbon cycle during the early part of the last deglaciation from 20,000 to 13,000 years before the present. The data synthesis will be accomplished through an international collaborative project (OC3: Ocean Circulation and Carbon Cycling). A newly developed global climate model that includes three-dimensional ocean physics, biogeochemical cycles, isotopes of carbon and nitrogen, and sediments will be constrained by the OC3 carbon isotope synthesis and other existing paleoceanographic datasets such as a recent synthesis of nitrogen isotope data and an ongoing radiocarbon compilation. The goal is to reconstruct quantitatively how ocean carbon storage was affected by different processes, such as the biological pump, sea ice cover, ocean circulation, stratification, iron fertilization, sea level and sediment interactions. The project has the potential to improve our understanding of the deglacial ocean circulation, its carbon cycling, and it may provide explanations for the rise in atmospheric CO2. Funding supports a postdoctoral researcher, and provides research opportunities for undergraduate students.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
Note:
When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external
site maintained by the publisher. Some full text articles may not yet be available without a
charge during the embargo (administrative interval).
Some links on this page may take you to non-federal websites. Their policies may differ from
this site.
PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Intellectual Merit
This project has investigated the global ocean′s carbon cycle and circulation during the last ice age (Last Glacial Maximum, ~20,000 years before the present) in order to better understand the low atmospheric CO2 concentrations during that time measured in ice cores. We have combined simulations with a three-dimensional ocean model that includes biogeochemistry and three isotopes (carbon-13, carbon-14, and nitrogen-15) with data from sea floor sediments. The model-data comparison suggests that the Atlantic Meridional Overturning Circulation (AMOC) was shallower and possibly weaker during the LGM and that iron fertilization in the Southern Ocean was enhanced due to increased dust deposition from the atmosphere. Whereas the data constrain AMOC depth well, they do not constrain its strength equally well and thus larger uncertainties in quantifying AMOC strength remain. We have created the first model of the LGM ocean consistent with the above sediment data and other reconstructions such as deep ocean oxygen and surface and whole ocean temperature. This model was subsequently used to diagnose the ocean′s carbon cycle and quantify its impact on atmospheric CO2. We found that ocean carbon storge was enhanced due to a greater disequilibrium between the surface ocean and the atmosphere, and not as previously suggested, because of a more efficient biological pump. The model explains more than three-quarter (67-87 ppm) of the observed atmospheric CO2 decrease of ~90 ppm during the LGM. We attribute most of the change (44-45 ppm) to cooling of ocean temperatures and increased iron fertilization (26-39 ppm), whereas circulation and sea ice changes played only minor roles. Results from this project have been published in 11 peer-reviewed publications and presented in scientific workshops and conferences.
Broader Impacts
An early career scientist (Dr. J. Muglia) has been supported and mentored. Dr. Muglia has made a successful transition to a research scientist position in Argentina. The project has fostered international collaboration by supporting the Ocean Circulation and Carbon Cycling (OC3) working group of the Past Global Changes (PAGES) project. OC3 has organized three workshops and supported participation by numerous early career scientists and scientists from developing countries. Data and model code from this project have been made publicly available. We have organized sessions at scientific meetings such as the Fall Meetings of the American Geophysical Union. The project has improved an existing climate model, developed a new method to diagnose ocean carbon storage, and generated new syntheses of sediment data, thus enhancing the research infrastructure.
Last Modified: 09/21/2020
Modified by: Andreas Schmittner
Please report errors in award information by writing to: awardsearch@nsf.gov.
