| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
|
| Initial Amendment Date: | August 12, 2014 |
| Latest Amendment Date: | August 12, 2014 |
| Award Number: | 1451120 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Henrietta Edmonds
hedmonds@nsf.gov (703)292-7427 OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
| Start Date: | June 1, 2014 |
| End Date: | September 30, 2017 (Estimated) |
| Total Intended Award Amount: | $320,631.00 |
| Total Awarded Amount to Date: | $320,631.00 |
| Funds Obligated to Date: |
|
| History of Investigator: |
|
| Recipient Sponsored Research Office: |
11200 SW 8TH ST MIAMI FL US 33199-2516 (305)348-2494 |
| Sponsor Congressional District: |
|
| Primary Place of Performance: |
FL US 33199-0001 |
| Primary Place of
Performance Congressional District: |
|
| Unique Entity Identifier (UEI): |
|
| Parent UEI: |
|
| NSF Program(s): | Chemical Oceanography |
| 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
In the ocean, trace elements function variously as nutrients, as contaminants from human activity, and even as convenient tracers of current and past oceanographic processes. Their biogeochemical cycling has major impacts on the ocean carbon cycle and ecosystem dynamics as well as on global climate change. Many processes influencing the distribution and behavior of trace elements in the ocean cannot be directly observed, so consequently a variety of geochemical tracers are used to provide important constraints on their rates and pathways. Beryllium-7 (Be7) is a cosmogenic (i.e., produced in the upper atmosphere) radionuclide that, because of its half-life (53.3d), can be used in the study of environmental processes occurring over seasonal timescales. This timescale is important to studies of biological production, nutrient regeneration, and atmospheric deposition, to name a few.
In this project, a research team from the University of Miami will make measurements of water column Be7 along the U.S.GEOTRACES transect from Peru to Tahiti in 2013. The mission of the International GEOTRACES Program (of which the US program is a component) is "to identify processes and quantify fluxes that control the distributions of key trace elements and isotopes in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions."
As part of the multi-institutional U.S.GEOTRACES Pacific campaign, the Miami team will address key tasks formulated within the GEOTRACES Science Plan. Specifically, they will: (1) provide realistic estimates of the underlying transport processes influencing measured trace elements of interest (TEI) distributions; they will use water column measurements of Be7 as a tracer of physical processes, such as mixing and upwelling, which redistribute biologically active species; and (2) develop and apply new Be7 methods for quantifying the atmospheric deposition of TEIs measured by other research teams participating in the campaign. Measurements of Be7 in the surface waters and in the lower atmosphere along the cruise track will provide estimates of the atmospheric input of relevant TEIs. The atmospheric input into the global ocean is an important budgetary component of numerous chemical species, yet is very difficult to constrain. The data generated in this work will be available to allow ground-truthing of aerosol deposition models and the atmospheric input of trace elements.
Broader impacts: The proposed work is in support of the GEOTRACES program, and as such contributes to many of the broad intellectual objectives of that program. The ability to provide estimates of the atmospheric input of relevant TEIs is an important example, and one that will contribute widely to the field in the future beyond GEOTRACES, including understanding anthropogenic impacts on the oceans. Education and training of graduate students will be essential components of this research.
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:
Summary:
Many processes in the ocean cannot be directly observed and as such, tracers are used to provide important constraints on their rates and pathways. Be-7 is a tracer that, because of its half-life (53.3d), allows the study of processes which occur over time (seasonal) and spatial (shallow thermocline) scales that are otherwise difficult to obtain but which are critically important to studies of biological production, nutrient regeneration, and atmospheric deposition, to name a few. However, it has been one that is difficult to approach due to the lack of oceanographic tracers suitable for integrating processes over this temporal range. Advances in sampling and analytical techniques, coupled with a better understanding of the behavior of 7Be in ocean biogeochemical cycles, present an opportunity to fully utilize this tracer and address key tasks formulated within the GEOTRACES science plan. In this work we provided realistic estimates of the underlying transport processes influencing measured trace element distributions, and provided estimates of the atmospheric deposition of trace elements.
Outcomes:
We participated in the 55 day Peru-Tahiti US GEOTRACES leg in November-December, 2013. All of our sampling objectives were met. This included collection of 13 water column profiles for 7Be and 17 high volume aerosol samples. All of these samples have been analyzed. In addition, we measured high volume size-distributed aerosol samples.
Our hypothesis that the 7Be inventories in the eastern section would reflect upwelling was proven. That is, the 7Be concentration in the usually 7Be-rich surface mixed layer was diluted from penetration of 7Be "dead" water upwelled from below. An obvious correlation between 7Be inventory and water temperature was observed; cold, upwelled water had a deficit of 7Be.
This dilution of surface 7Be with upwelled water provides a means to infer upwelling rates. Furthermore, with knowledge of upwelling rates, 7Be profiles were used to constrain vertical diffusivity within the upper thermocline. The PI has presented these results at the AGU meeting in December, 2014.
In addition, the results were published in a peer-reviewed journal, Global Biogeochemical Cycles. In this work, the transport parameters derived from 7Be were used with nitrate profiles to calculate net community production.
Finally, the 7Be aerosol concentrations are being applied to trace element aerosol concentrations to derive the flux of trace elements to the ocean of this study region.
The derived transport parameters have been used by other PIs ion the program who have thus far used the information to interpret Hg, 234Th, POC flux, redox behavior, and nitrate flux along that expedition transect.
Broader Impacts:
The derivation of upwelling rates with vertical diffusion parameters enables calculation of new primary production. This could be important in economic fisheries, and social disciplines.
The use of 7Be to derive the atmospheric input of trace elements(TE) offers robust estimates of TE input to the surface ocean averaged over several weeks and over a sub-regional to regional spatial scale. The method is particularly useful for remote areas where fixed sampling stations do not exist; that is, the majority of the global ocean. The study of marine trace element geochemistry in general and the study of micronutrient (e.g., Fe, Mn, Zn) biogeochemistry in marine ecology will benefit greatly from this method.
All data has been reported to, and is accessible in, the Biological and Chemical Oceanography Data Management Office (BCO-DMO).
Last Modified: 10/02/2017
Modified by: David C Kadko
Please report errors in award information by writing to: awardsearch@nsf.gov.
