Temporal Evolution of Tritium-3He Age in the North Atlantic: Implications for Thermocline Ventilation
This thesis studies the physical mechanisms which ventilate the subtropical thermocline of the eastern North Atlantic. The coupled transient tracers tritium and 3He define a tracer age diagnostic which estimates the elapsed time since a water parcel was resident at the ocean surface. Analysis of the...
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ftdtic:ADA333231 2023-05-15T17:29:21+02:00 Temporal Evolution of Tritium-3He Age in the North Atlantic: Implications for Thermocline Ventilation Robbins, Paul E. WOODS HOLE OCEANOGRAPHIC INSTITUTION MA 1997-09 text/html http://www.dtic.mil/docs/citations/ADA333231 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA333231 en eng http://www.dtic.mil/docs/citations/ADA333231 APPROVED FOR PUBLIC RELEASE DTIC AND NTIS Physical and Dynamic Oceanography *HELIUM *THERMOCLINES *TRITIUM OCEAN SURFACE VENTILATION NUMERICAL ANALYSIS THESES FLOW FIELDS DIFFUSION HYPOTHESES HYDROGRAPHY GEOSTROPHIC CURRENTS GEOSTROPHIC WIND NORTH ATLANTIC OCEAN ADVECTION *THERMOCLINE VENTILATION Text 1997 ftdtic 2016-02-19T21:17:49Z This thesis studies the physical mechanisms which ventilate the subtropical thermocline of the eastern North Atlantic. The coupled transient tracers tritium and 3He define a tracer age diagnostic which estimates the elapsed time since a water parcel was resident at the ocean surface. Analysis of the historical database of 3He and tritium measurements reveals large, systematic changes in the observed tracer age. The first hypothesis examined is that the observed shift in tracer age results from a weakening of the physical ventilation. Examination of a time-series of the meridional geostrophic velocity and the large-scale oxygen distribution, both based on historical hydrography, reveal no evidence for such a change. Therefore, the temporal trend in observed tritium-3He age cannot be explained by an alteration of the physical ventilation of the thermocline. A second hypothesis is that the temporal change in the tritium-3He age field reflects a signal of the tritium invasion itself. Numerical simulations of the thermocline ventilation of 3H and 3He are performed to examine the steadiness of the tracer age field under different advective-diffusive regimes. The temporal behavior of the tracer age field is dependent on the relative importance of the advection and diffusion of the flow field. The observed temporal behavior of the tracer age field is evidence of a significant role for lateral mixing in the ventilation of the thermocline. Text North Atlantic Defense Technical Information Center: DTIC Technical Reports database |
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Defense Technical Information Center: DTIC Technical Reports database |
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English |
topic |
Physical and Dynamic Oceanography *HELIUM *THERMOCLINES *TRITIUM OCEAN SURFACE VENTILATION NUMERICAL ANALYSIS THESES FLOW FIELDS DIFFUSION HYPOTHESES HYDROGRAPHY GEOSTROPHIC CURRENTS GEOSTROPHIC WIND NORTH ATLANTIC OCEAN ADVECTION *THERMOCLINE VENTILATION |
spellingShingle |
Physical and Dynamic Oceanography *HELIUM *THERMOCLINES *TRITIUM OCEAN SURFACE VENTILATION NUMERICAL ANALYSIS THESES FLOW FIELDS DIFFUSION HYPOTHESES HYDROGRAPHY GEOSTROPHIC CURRENTS GEOSTROPHIC WIND NORTH ATLANTIC OCEAN ADVECTION *THERMOCLINE VENTILATION Robbins, Paul E. Temporal Evolution of Tritium-3He Age in the North Atlantic: Implications for Thermocline Ventilation |
topic_facet |
Physical and Dynamic Oceanography *HELIUM *THERMOCLINES *TRITIUM OCEAN SURFACE VENTILATION NUMERICAL ANALYSIS THESES FLOW FIELDS DIFFUSION HYPOTHESES HYDROGRAPHY GEOSTROPHIC CURRENTS GEOSTROPHIC WIND NORTH ATLANTIC OCEAN ADVECTION *THERMOCLINE VENTILATION |
description |
This thesis studies the physical mechanisms which ventilate the subtropical thermocline of the eastern North Atlantic. The coupled transient tracers tritium and 3He define a tracer age diagnostic which estimates the elapsed time since a water parcel was resident at the ocean surface. Analysis of the historical database of 3He and tritium measurements reveals large, systematic changes in the observed tracer age. The first hypothesis examined is that the observed shift in tracer age results from a weakening of the physical ventilation. Examination of a time-series of the meridional geostrophic velocity and the large-scale oxygen distribution, both based on historical hydrography, reveal no evidence for such a change. Therefore, the temporal trend in observed tritium-3He age cannot be explained by an alteration of the physical ventilation of the thermocline. A second hypothesis is that the temporal change in the tritium-3He age field reflects a signal of the tritium invasion itself. Numerical simulations of the thermocline ventilation of 3H and 3He are performed to examine the steadiness of the tracer age field under different advective-diffusive regimes. The temporal behavior of the tracer age field is dependent on the relative importance of the advection and diffusion of the flow field. The observed temporal behavior of the tracer age field is evidence of a significant role for lateral mixing in the ventilation of the thermocline. |
author2 |
WOODS HOLE OCEANOGRAPHIC INSTITUTION MA |
format |
Text |
author |
Robbins, Paul E. |
author_facet |
Robbins, Paul E. |
author_sort |
Robbins, Paul E. |
title |
Temporal Evolution of Tritium-3He Age in the North Atlantic: Implications for Thermocline Ventilation |
title_short |
Temporal Evolution of Tritium-3He Age in the North Atlantic: Implications for Thermocline Ventilation |
title_full |
Temporal Evolution of Tritium-3He Age in the North Atlantic: Implications for Thermocline Ventilation |
title_fullStr |
Temporal Evolution of Tritium-3He Age in the North Atlantic: Implications for Thermocline Ventilation |
title_full_unstemmed |
Temporal Evolution of Tritium-3He Age in the North Atlantic: Implications for Thermocline Ventilation |
title_sort |
temporal evolution of tritium-3he age in the north atlantic: implications for thermocline ventilation |
publishDate |
1997 |
url |
http://www.dtic.mil/docs/citations/ADA333231 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA333231 |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
DTIC AND NTIS |
op_relation |
http://www.dtic.mil/docs/citations/ADA333231 |
op_rights |
APPROVED FOR PUBLIC RELEASE |
_version_ |
1766123260544548864 |