| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
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| Initial Amendment Date: | August 2, 2013 |
| Latest Amendment Date: | August 27, 2014 |
| Award Number: | 1338814 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Simone Metz
OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
| Start Date: | September 1, 2013 |
| End Date: | January 31, 2020 (Estimated) |
| Total Intended Award Amount: | $4,840,000.00 |
| Total Awarded Amount to Date: | $4,840,000.00 |
| Funds Obligated to Date: |
FY 2014 = $2,930,000.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
77 MASSACHUSETTS AVE CAMBRIDGE MA US 02139-4301 (617)253-1000 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
77 Mass. Ave., 54-1520 Cambridge MA US 02139-4307 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Front in Earth Sys Dynamics |
| Primary Program Source: |
01001415DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
The dramatic depletion of the Antarctic ozone since the late 1970s has introduced a major perturbation to the radiative balance of the stratosphere with a wide range of consequences for climate. There is strong evidence that ozone loss has significantly altered the climate of the southern hemisphere troposphere, including the surface, with implications for ocean circulation, the cryosphere and coupled carbon cycle. As ozone depletion recovers in the next half-century or so, a corresponding reversal of these changes can be expected, providing an unprecedented opportunity to observe how the climate system relaxes from a known perturbation. The effort proposed here focuses on improving the understanding of current southern hemisphere climate changes linked to ozone depletion, so that we can better prepare to maximize the learning experience represented by the future healing of the ozone hole through identification of mechanisms, impacts, and observable indicators.
The Southern Hemisphere is of huge importance to the trajectory of the global climate system and presents a fascinating intellectual and modeling challenge involving interdisciplinary study of the coupling of the stratosphere, troposphere and ocean; coupling of chemistry, radiation and dynamics in the stratosphere; coupling of the ocean, ice and atmosphere at the earth?s surface; the coupling of the carbon cycle to ocean dynamics. The problem is multiscale and multi-component that requires the bringing together of atmospheric chemistry, ocean biogeochemistry, sea-ice dynamics together with atmospheric and ocean dynamics and transport.
To tackle this problem we have assembled an interdisciplinary team of researchers from MIT, Columbia University, Johns Hopkins University and NCAR, whose expertise covers the above areas. A suite of models of different complexity will be deployed to explore the mechanisms, impacts and indicators of the Antarctic stratospheric ozone hole and its recovery on the climate of the atmosphere-oceanice- carbon system. To this end we will explore: (i) how interactive chemistry modifies the coupling between the stratospheric vortex and the rest of the climate system (ii) resulting changes in ocean circulation, ice cover, heat and carbon uptake, and biogeochemistry of the southern ocean (iii) the impacts and observable indicators of the ozone hole on the global climate.
Intellectual merit
The problem outlined here is one of the most challenging in climate science demanding the development and deployment of a modeling hierarchy that arcs from the stratosphere to the interior ocean and couples chemistry, radiation, fluid dynamics, ice dynamics and the carbon cycle. Moreover, it is one that is amenable to study in the context of the instrumental record. An important product of the study is to make an initial list of climate indicators that could be used to monitor the rebound of SH climate from the ozone hole and its evolution over the next few decades in the presence of ever increasing greenhouse gas forcing.
Broader Impacts
We will extend ongoing activity at MIT and Northeastern University in which K-12 teachers are educated about climate science in the context of national science curriculum development and include some of these activities in K-12 programs at JHU and Columbia. We also propose to host and engage in our research and educational activities Summer Research Program (MSRP) students at MIT, an institutional effort that facilitates the involvement of talented students in engineering and science research, particularly those from underrepresented groups. Finally we propose to engage the broad science community on southern hemisphere climate change through two workshops, including developing a community view on indicators and needed observations.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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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.
The ‘Ozone and Climate’ Project was an ambitious study funded by the Frontiers in Earth System Dynamics program of NSF. An interdisciplinary team from MIT, Columbia, Johns Hopkins and the NCAR aimed to leverage an unprecedented opportunity to understand the effect of the Antarctic ozone hole on global climate. We were able to examine the fundamental robustness of the climate system as it reacts to and recovers from the ozone hole, while simultaneously responding to the steadily accelerating increase in global greenhouse gas concentrations.
The project was organized around three main themes:
1. How does interactive chemistry modify coupling between the stratospheric vortex and the rest of the climate system?
Most climate models specify stratospheric ozone using monthly mean, zonal mean values and linearly interpolate to the time resolution of the model. We showed that this method leads to significant biases in the simulated SH climate due to under sampling of the rapid temporal changes in ozone during the seasonal evolution of the Antarctic ozone hole. Our results suggest that the bias can be substantially reduced by specifying a daily ozone concentration.
2. How are ocean circulation, ice cover, heat and carbon uptake and biogeochemistry impacted by the ozone hole?
(i) Computing climate response functions to step-changes in ozone forcing
We showed that Antarctic sea surface temperatures (SSTs) will respond differently at different time scales to the annual opening and closing of the ozone hole. Initially, cooler summer SSTs induced by enhanced northward Ekman drift will likely lead to early winter freezing and expanding sea ice coverage. Later, over years to decades, we anticipate that SSTs will slowly warm overall in response to upwelling of warm water from the interior ocean driven by stronger westerly winds leading to reductions in sea ice extent year-round.
(ii) Antarctic Sea Ice
Over the last 40 years the total Antarctic sea ice cover exhibited a small but significant linear increase. We showed that this small increase is the result of much larger, but partially compensating trends on regional scales. Large increases in the Ross and Weddell Seas have been offset by large declines in the Amundsen-Bellingshausen Sea, with both trends being maximum in austral fall. We assessed the potential role of Antarctic stratospheric ozone loss and associated atmospheric circulation for regional sea ice variations. Ozone depletion contributes to a positive trend in the austral summer zonal winds which projects onto a deepening of the Amundsen Sea Low with potential impacts on regional ice variations.
(iii) Impacts of ozone depletion on ocean circulation, carbon uptake and biogeochemistry.
Observations show robust changes in the circulation of the Southern Ocean in recent decades. Using a hierarchy of models, we showed that increases in ozone-depleting substances during the late 20th Century are likely to have been an important driver of these changes, causing a poleward shift of the ocean's meridional overturning circulation as well as changes in temperature and salinity. We also found that differences between various Earth System models in how Southern Ocean winds trends are simulated may be less important for carbon uptake than differences in how mesoscale eddies and their mixing and stirring are parameterized.
3. Impact of the ozone hole and its recovery on observable indicators.
Three decades of data indicate strong correspondence between high levels of stratospheric ozone over Antarctica during November with unusually warm, dry and heat wave prone summers in mid-latitude areas of Australia, South America and Africa. We explored how this relationship could potentially be exploited to enhance extended summer weather forecasting for these areas.
Observations show robust near-surface trends in Southern Hemisphere tropospheric circulation towards the end of the twentieth century, including a poleward shift in the mid-latitude jet, a positive trend in the Southern Annular Mode, and an expansion of the Hadley cell. It has been established that these trends were driven by ozone depletion in the Antarctic stratosphere due to emissions of ozone-depleting substances. We showed that these widely reported circulation trends paused, or slightly reversed, around the year 2000. Because pre-2000 circulation trends have affected precipitation, ocean circulation and salinity, we anticipate that a pause in these trends will have wider impacts on the Earth system. Signatures of the effects of the Montreal Protocol and the associated stratospheric ozone recovery might therefore manifest, or have already manifested, in other aspects of the Earth system.
Our project involved graduate students and postdoctoral researchers, outreach activities, and strong synergies with international activities. Eight graduate students, and seven postdoctoral researchers worked on the project. Over 60 peer-reviewed research papers were written over the 6-year period of the project. A summary of the project can be found here: http://ozoneandclimate.squarespace.com/
Last Modified: 04/27/2020
Modified by: John C Marshall
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