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Iodine isotopes species fingerprinting environmental conditions in surface water along the northeastern Atlantic Ocean.

He P, Hou X, Aldahan A, Possnert G, Yi P - Sci Rep (2013)

Bottom Line: The results show iodate as the predominant species in the analyzed marine waters for both (127)I and (129)I.Despite the rather constant ratios of (127)I(-)/(127)IO3(-), the (129)I(-)/(129)IO3(-) values reveal variations that apparently response to sources, environmental conditions and residence time.These findings provide a new tracer approach that will strongly enhance the application of anthropogenic (129)I in ocean environments and impact on climate at the ocean boundary layer.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Geochemistry, Chengdu University of Technology, Chengdu 610059, China [2] Department of Earth Sciences, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden.

ABSTRACT
Concentrations and species of iodine isotopes ((127)I and (129)I) provide vital information about iodine geochemistry, environmental conditions and water masses exchange in oceans. Despite extensive investigations of anthropogenic (129)I in the Arctic Ocean and the Nordic Seas, concentrations of the isotope in the Atlantic Ocean are, however, still unknown. We here present first data on (129)I and (127)I, and their species (iodide and iodate) in surface water transect along the northeastern Atlantic between 30° and 50°N. The results show iodate as the predominant species in the analyzed marine waters for both (127)I and (129)I. Despite the rather constant ratios of (127)I(-)/(127)IO3(-), the (129)I(-)/(129)IO3(-) values reveal variations that apparently response to sources, environmental conditions and residence time. These findings provide a new tracer approach that will strongly enhance the application of anthropogenic (129)I in ocean environments and impact on climate at the ocean boundary layer.

No MeSH data available.


Concentrations of 129I (108 atoms/L) along the transect and suggested surface 129I pathways from the English Channel and the Strait of Gibraltar (dashed arrows).Red regions represent major coastal upwelling and solid blue lines show the spread pathways of deep Mediterranean water. Major nuclear reprocessing facilities (NRFs) are marked as stars. The original map was constructed by a free software Ocean Data View (ODV 4.5.3).
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f4: Concentrations of 129I (108 atoms/L) along the transect and suggested surface 129I pathways from the English Channel and the Strait of Gibraltar (dashed arrows).Red regions represent major coastal upwelling and solid blue lines show the spread pathways of deep Mediterranean water. Major nuclear reprocessing facilities (NRFs) are marked as stars. The original map was constructed by a free software Ocean Data View (ODV 4.5.3).

Mentions: Saline and dense Mediterranean Outflow Water (MOW) that passes through the Strait of Gibraltar descends as Mediterranean Undercurrent in the Gulf of Cadiz along the continental slope and interacts with local bottom topography, and spreads towards the Azores, the Canary Islands and the coast of Portugal31. Two major Mediterranean cores with maxima in the temperature and salinity can be well detected in the depth of 800 and 1200 m32. This feature is also shown by two peaks of 129I/127I ratio in a water profile taken from the northeastern Atlantic Ocean33. The dense Mediterranean Water typically settles at depth of 800–1200 m in the North Atlantic Ocean, which is physically separated by a salinity-minimum layer of Subpolar Mode Water (S < 36) above34. The isolated Mediterranean layer should not have direct influence on the surface and the North Atlantic Central Water (NACW) that control the surface circulation. Thus, those high 129I samples (>2 × 108 atoms/L) in the south of our transect seem to originate from the Gulf of Cadiz and Portugal coast rather than local upwelling effect in the open sea. Intensive in situ hydrographic data and sea surface temperature (SST) satellite observations, as well as numerical models reveal that the eastward Azores Current, combined with equatorial Portuguese Current that flows parallel to the west Iberia coast, enters the Gulf of Cadiz along the continental slope towards the Strait of Gibraltar. The easternmost part of this anticyclonic circulation eventually feeds the Canary Current (Fig. 1c). This general feature of circulation pattern was thought to be weakened in winter and enhanced in summer353637. Mediterranean Outflow Water (MOW) overflows the sills of Gibraltar in a shallow depth (~200 m) and intense local vertical mixing and entrainment processes taken place at the mouth of the strait are even capable to induce and maintain the eastward surface Azores Current3839. Mauritzen et al.40 hypothesized a cross-isopycnal MOW towards the surface in the vicinity of the Strait of Gibraltar, which they referred to ‘detrainment’ process and later confirmed by a rotating tank experiment. Thus the high 129I concentration may occur in the surface water as a result of Mediterranean water upwelled in this turbulent and instable fluid condition within the eastern Gulf of Cadiz. In addition to the double-core structure of the MOW, a shallow layer is identified through salinity and temperature field at depths between 400 m and 700 m36,41, or depicted in the geostrophic velocity field4243 along the upper continental slope of the Gulf of Cadiz and off the southern half of the Iberian western coast4144. Therefore, upwarping of this Mediterranean shallow core, in association of coastal upwelling that is especially occurring off the Capes St. Vicente and St. Maria, by favored westerlies during summer45, probably bring the Mediterranean-labeled 129I from mid-depth to the surface. Accordingly, we suggest the surface water in location 24 and 25 may reflect the propagation of a branch of this onshore water westwards towards the open ocean after leaving Cape St. Vicente when easterlies dominated (Fig. 4). Seasonal and regional variations of wind system in the transition zone between westerlies and trade wind highly influences the surface circulation pattern in most parts of our sampling transect. Based on buoy and hydrographic data, large-scale movement of upper water between subpolar and subtropical gyres is week, flowing slowly towards east and south46. However, a poleward surface current has been reported off the west coast of Portugal during winter when the wind blowing northward47. Although the origin and variability of this slope-flow current is still unclear, it may be connected with the coastal counter flow in the western of Cadiz, which flow anticyclonically around Cape St. Vicente and thus bearing high 129I signal from MOW48. When this water reaches the Cape Espichel, local coastal morphology, shelf/slope bathymetry as well as propagation of eddies make the 129I plume extends seaward, which is reflected in our sample 17. The other two high-129I samples, which occur in the middle of Madeira and African coast (location 32 and 33), however, are likely related to the onshore flow of Canary Current, which with one branch separated from the northern Morocco coast37, transports 129I from the Strait of Gibraltar to further west around 14°W (Fig. 4).


Iodine isotopes species fingerprinting environmental conditions in surface water along the northeastern Atlantic Ocean.

He P, Hou X, Aldahan A, Possnert G, Yi P - Sci Rep (2013)

Concentrations of 129I (108 atoms/L) along the transect and suggested surface 129I pathways from the English Channel and the Strait of Gibraltar (dashed arrows).Red regions represent major coastal upwelling and solid blue lines show the spread pathways of deep Mediterranean water. Major nuclear reprocessing facilities (NRFs) are marked as stars. The original map was constructed by a free software Ocean Data View (ODV 4.5.3).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3842550&req=5

f4: Concentrations of 129I (108 atoms/L) along the transect and suggested surface 129I pathways from the English Channel and the Strait of Gibraltar (dashed arrows).Red regions represent major coastal upwelling and solid blue lines show the spread pathways of deep Mediterranean water. Major nuclear reprocessing facilities (NRFs) are marked as stars. The original map was constructed by a free software Ocean Data View (ODV 4.5.3).
Mentions: Saline and dense Mediterranean Outflow Water (MOW) that passes through the Strait of Gibraltar descends as Mediterranean Undercurrent in the Gulf of Cadiz along the continental slope and interacts with local bottom topography, and spreads towards the Azores, the Canary Islands and the coast of Portugal31. Two major Mediterranean cores with maxima in the temperature and salinity can be well detected in the depth of 800 and 1200 m32. This feature is also shown by two peaks of 129I/127I ratio in a water profile taken from the northeastern Atlantic Ocean33. The dense Mediterranean Water typically settles at depth of 800–1200 m in the North Atlantic Ocean, which is physically separated by a salinity-minimum layer of Subpolar Mode Water (S < 36) above34. The isolated Mediterranean layer should not have direct influence on the surface and the North Atlantic Central Water (NACW) that control the surface circulation. Thus, those high 129I samples (>2 × 108 atoms/L) in the south of our transect seem to originate from the Gulf of Cadiz and Portugal coast rather than local upwelling effect in the open sea. Intensive in situ hydrographic data and sea surface temperature (SST) satellite observations, as well as numerical models reveal that the eastward Azores Current, combined with equatorial Portuguese Current that flows parallel to the west Iberia coast, enters the Gulf of Cadiz along the continental slope towards the Strait of Gibraltar. The easternmost part of this anticyclonic circulation eventually feeds the Canary Current (Fig. 1c). This general feature of circulation pattern was thought to be weakened in winter and enhanced in summer353637. Mediterranean Outflow Water (MOW) overflows the sills of Gibraltar in a shallow depth (~200 m) and intense local vertical mixing and entrainment processes taken place at the mouth of the strait are even capable to induce and maintain the eastward surface Azores Current3839. Mauritzen et al.40 hypothesized a cross-isopycnal MOW towards the surface in the vicinity of the Strait of Gibraltar, which they referred to ‘detrainment’ process and later confirmed by a rotating tank experiment. Thus the high 129I concentration may occur in the surface water as a result of Mediterranean water upwelled in this turbulent and instable fluid condition within the eastern Gulf of Cadiz. In addition to the double-core structure of the MOW, a shallow layer is identified through salinity and temperature field at depths between 400 m and 700 m36,41, or depicted in the geostrophic velocity field4243 along the upper continental slope of the Gulf of Cadiz and off the southern half of the Iberian western coast4144. Therefore, upwarping of this Mediterranean shallow core, in association of coastal upwelling that is especially occurring off the Capes St. Vicente and St. Maria, by favored westerlies during summer45, probably bring the Mediterranean-labeled 129I from mid-depth to the surface. Accordingly, we suggest the surface water in location 24 and 25 may reflect the propagation of a branch of this onshore water westwards towards the open ocean after leaving Cape St. Vicente when easterlies dominated (Fig. 4). Seasonal and regional variations of wind system in the transition zone between westerlies and trade wind highly influences the surface circulation pattern in most parts of our sampling transect. Based on buoy and hydrographic data, large-scale movement of upper water between subpolar and subtropical gyres is week, flowing slowly towards east and south46. However, a poleward surface current has been reported off the west coast of Portugal during winter when the wind blowing northward47. Although the origin and variability of this slope-flow current is still unclear, it may be connected with the coastal counter flow in the western of Cadiz, which flow anticyclonically around Cape St. Vicente and thus bearing high 129I signal from MOW48. When this water reaches the Cape Espichel, local coastal morphology, shelf/slope bathymetry as well as propagation of eddies make the 129I plume extends seaward, which is reflected in our sample 17. The other two high-129I samples, which occur in the middle of Madeira and African coast (location 32 and 33), however, are likely related to the onshore flow of Canary Current, which with one branch separated from the northern Morocco coast37, transports 129I from the Strait of Gibraltar to further west around 14°W (Fig. 4).

Bottom Line: The results show iodate as the predominant species in the analyzed marine waters for both (127)I and (129)I.Despite the rather constant ratios of (127)I(-)/(127)IO3(-), the (129)I(-)/(129)IO3(-) values reveal variations that apparently response to sources, environmental conditions and residence time.These findings provide a new tracer approach that will strongly enhance the application of anthropogenic (129)I in ocean environments and impact on climate at the ocean boundary layer.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Geochemistry, Chengdu University of Technology, Chengdu 610059, China [2] Department of Earth Sciences, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden.

ABSTRACT
Concentrations and species of iodine isotopes ((127)I and (129)I) provide vital information about iodine geochemistry, environmental conditions and water masses exchange in oceans. Despite extensive investigations of anthropogenic (129)I in the Arctic Ocean and the Nordic Seas, concentrations of the isotope in the Atlantic Ocean are, however, still unknown. We here present first data on (129)I and (127)I, and their species (iodide and iodate) in surface water transect along the northeastern Atlantic between 30° and 50°N. The results show iodate as the predominant species in the analyzed marine waters for both (127)I and (129)I. Despite the rather constant ratios of (127)I(-)/(127)IO3(-), the (129)I(-)/(129)IO3(-) values reveal variations that apparently response to sources, environmental conditions and residence time. These findings provide a new tracer approach that will strongly enhance the application of anthropogenic (129)I in ocean environments and impact on climate at the ocean boundary layer.

No MeSH data available.