Salinity Surface Layer Research Articles

Surface Layer Salinity of Young Sea Ice

The high-salinity surface layer of young sea ice was subjected to field and laboratory experiments. Artificial pools, in which young ice was formed, were opened within a fast-ice sheet in the Saroma lagoon, Hokkaido, in February of 1983 and 1984. The salinity of 1 mm thick surface layer of the young ice was observed as high as 42.4‰, which exceeds the seawater salinity of 31‰. The surface salinity increased with rising surface temperature. When a load was placed on the fast ice near the pool, seeped brine of salinity 72.5‰ was observed on the surface of the young ice; and when the load was removed, the brine disappeared. Meanwhile, brine permeabilities, both upward and downward, were measured in the laboratory, Both permeabilities decreased logarithmically with lowering surface temperature. A remarkable anisotropy was observed: the upward permeability was greater than downward, and the ratio of upward to downward premeability increased with lowering surface temperature from 5 at -3 °C to 33 at -5°C. Upward and downward permeabilities in ms-1 were respectively 1x10-4 and 2x10-5 at -3°C, 2x10-5 and 6x10-7 at -5°C, and at -10°C upward permeability was 3x10-7.

Surface Layer Salinity of Young Sea Ice

The high-salinity surface layer of young sea ice was subjected to field and laboratory experiments. Artificial pools, in which young ice was formed, were opened within a fast-ice sheet in the Saroma lagoon, Hokkaido, in February of 1983 and 1984. The salinity of 1 mm thick surface layer of the young ice was observed as high as 42.4‰, which exceeds the seawater salinity of 31‰. The surface salinity increased with rising surface temperature. When a load was placed on the fast ice near the pool, seeped brine of salinity 72.5‰ was observed on the surface of the young ice; and when the load was removed, the brine disappeared. Meanwhile, brine permeabilities, both upward and downward, were measured in the laboratory, Both permeabilities decreased logarithmically with lowering surface temperature. A remarkable anisotropy was observed: the upward permeability was greater than downward, and the ratio of upward to downward premeability increased with lowering surface temperature from 5 at -3 °C to 33 at -5°C. Upward and downward permeabilities in ms-1 were respectively 1x10-4 and 2x10-5 at -3°C, 2x10-5 and 6x10-7 at -5°C, and at -10°C upward permeability was 3x10-7.

Anoxic events in the Mediterranean Sea in relation to the evolution of late Neogene climates

Stable isotopic and micropaleontological studies were made of selected sapropels (organic-rich sediments) deposited in the Mediterranean Sea during the last 5.0 m.y. to determine the processes responsible for their formation. Distinct isotopic and faunal changes occur across sapropels of late Pleistocene, early Pleistocene and latest Pliocene age, while smaller isotopic changes and more stable faunal assemblages are associated with the early and mid-late Pliocene sapropels. The large δ 18O depletions and euryhaline fauna associated with latest Pliocene—Pleistocene sapropels supports a density stratification model with a low salinity surface layer. In contrast, early Pliocene and mid-late Pliocene sapropels appear to have been formed as the result of sluggish circulation and low oxygen contents in bottom waters of the eastern Mediterranean due to the stable, warm climatic conditions of that time period.

River plumes, Coral Reefs and mixing in the Gulf of Papua and the northern Great Barrier Reef

The mean annual freshwater discharge in the Gulf of Papua, principally from the Fly, Kikori and Purari rivers, is estimated to be 13000 m3 s−1. Water from these rivers forms a low salinity surface layer in the Gulf, where it has a residence time of about two months and flows generally eastward. A small fraction of this water intrudes through Bligh Entrance on the Great Barrier Reef continental shelf. Horizontal patchiness and mixing of these intruding waters with shelf waters are considerably enhanced by secondary circulation (wakes) around coral reefs. The wakes shapes, visible in enhanced LANDSAT imagery, are similar to those around cylinders and plates in laboratory experiments at low Reynolds numbers. Topographically enhanced mixing may explain why the cross-shelf gradients of temperature and of the structure of fish communities are smaller in the northern region than in the central region of the Great Barrier Reef.

Faunal and oxygen isotopic evidence for surface water salinity changes during sapropel formation in the eastern Mediterranean

The discovery of widespread anaerobic deposits (sapropels) in late Cenozoic sediments of the eastern Mediterrenean has prompted many workers to propose the periodic occurrence of extremely low surface salinities in the Mediterranean. Oxygen isotopic determinations and total faunal analyses were made at 1000-year intervals across two equivalent sapropels in two piston cores from the Levatine Basin. The sapropel layers were deposited approximately 9000 y.B.P. (Sapropel A) and 80,000 y.B.P. (Sapropel B). Significant isotopic anomalies were recorded by the foraminiferal species within Sapropels A and B in both cores. The surface dwelling species record a larger 18O depletion than the mesopelagic species suggesting that surface salinities were reduced by 2–3% during sapropel formation. The faunal changes associated with the sapropels also indicate that the oceanographic conditions which lead to anoxic conditions in the eastern Mediterranean involve the formation of a low salinity surface layer. The source of the low salinity water might be meltwater produced by disintegration of the Fennoscandian Ice Sheet which drained into the Black Sea, into the Aegean Sea and finally into the eastern Mediterranean.

Injection events in ocean history

The reconnection, with the world ocean, of temporarily isolated ocean basins results in injection either of hyper-saline waters favouring abyssal stratification and stagnation, or of brackish Waters from high latitudes leading to a low salinity surface layer. Mass extinctions and sudden climatic change are closely associated with Arctic injection.

Response and Recovery of an Estuary Following a River Flood

ABSTRACT Tropical Storm Agnes produced a fourfold stress on the Rappahannock Estuary: first a storm tide, then river flooding and high sediment influx, followed by freshened inflow through the mouth. As flood energy dissipated through the upper estuary it broke down the normal partly-mixed regime and changed the near-bed transport direction from landward to seaward. Flooding of the lower estuary changed the partly-mixed regime to a salt-wedge and triggered a sequence of hydraulic events: (1) initial response, (2) shock, (3) rebound, (4) reversal, (5) second shock, (6) homogeneity and recovery. Net velocity and sediment transport returned to normal rates within 15 days whereas salinity recovered within 60 days. Despite high inflow, morphological changes were surprisingly small. The flood energy mainly produced a large transport of suspended sediment within the estuary. Most flood-borne sediment supplied during early flood stages was trapped landward of the fresh-salt water convergence which acted as a dynamic barrier. Sediment that escaped farther seaward in the low salinity surface layer during late flood stages was entrapped by the closed estuarine circulation which was strengthened and retained in the estuary during all stages of flooding. Of the total sediment influx, about 90% was trapped within the estuary and deposited mainly in the zone of the turbidity maximum.

Seston transport and deposition in Pelorus sound, south Island, New Zealand

Abstract Transport of seston (suspended sediment) in Pelorus Sound is controlled by tides and freshwater inflow. During high freshwater inflow, a moderately stratified estuarine circulation may be superimposed on the tidal circulation, but the latter dominates and transports seston seawards and landwards with the ebb and flood phases respectively. With extreme freshwater inflow, the estuarine circulation gains impetus and most seston is rapidly transported seaward in the low saline surface layer. Irrespective of circulation there is a persistent trend in seston concentrations. Highest values occur at the sound's head because of the influence of nearby Pelorus and Kaituna Rivers and because of resuspension of bottom sediment by strong tidal currents. Seston concentrations wane along the sound until near the entrance, where values increase as a result of greater production of biogenic seston and because additional seston is brought in from Cook Strait with the flood tide. This trend parallels variability in...