Mixing of Burdekin River flood waters in the Great Barrier Reef

1983 ◽  
Vol 34 (1) ◽  
pp. 49 ◽  
Author(s):  
E Wolanski ◽  
Senden D Van
Keyword(s):  
Continental Shelf ◽  
Great Barrier Reef ◽  
Low Frequency ◽  
Barrier Reef ◽  
River Plumes ◽  
Sea Floor ◽  
Longshore Currents ◽  
River Flood ◽  
Shelf Wave ◽  
River Floods

Wind fluctuations in the central region of the Great Barrier Reef from December 1980 to February 1981 generated low-frequency, reversing, longshore currents superimposed on the northward longshore currents initially generated both by intense direct rainfall over the continental shelf and by Burdekin River floods. The river plumes, which account for terrigenous mud distribution on the sea floor, were swept over the Great Barrier Reef. It is suggested that intense direct rainfall over the continental shelf and Burdekin River floods may create a barotropic shelf wave.

Water circulation and shelf waves in the northern Great Barrier Reef lagoon

1981 ◽  
Vol 32 (5) ◽  
pp. 721 ◽  
Author(s):  
E Wolanski ◽  
B Ruddick
Keyword(s):  
Great Barrier Reef ◽  
Sea Level ◽  
Low Frequency ◽  
Current Data ◽  
Barrier Reef ◽  
Sea Levels ◽  
The North ◽  
Level Data ◽  
Shelf Wave ◽  
Salinity Water

Currents and sea levels were measured at a number of locations in the Great Barrier Reef (GBR) lagoon from about 10 to 13� S., during the period October-December 1979. A strong non-tidal, low-frequency modulation of all sea-level and current data was found. The currents nearshore were driven northward by the wind, and then at least partially blocked by the dense network of reefs to the north of 10� s. The water then flowed southward in deeper water adjacent to the reef, driven by a longshore pressure gradient. The low- frequency sea-level data, though not the current records, showed northward phase propagation at speeds characteristic of a first-mode shelf wave trapped in the lagoon between the shore and the reef. Data are presented revealing the intrusion of low-salinity water, through Bligh Entrance, in the GBR lagoon, as a result of river discharges in the Gulf of Papua. It is suggested that low-frequency longshore currents may periodically flush these river plumes from the GBR lagoon and enhance interaction between reefs. In the Coral Sea in front of reef passages, the large horizontal velocities may result in forces upwelling by selective withdrawal and jet entrainment.

Continental shelf waves and their influence on the circulation around the Great Barrier Reef

1983 ◽  
Vol 34 (1) ◽  
pp. 23 ◽  
Author(s):  
E Wolanski ◽  
AF Bennett
Keyword(s):  
Continental Shelf ◽  
Great Barrier Reef ◽  
Sea Level ◽  
Atmospheric Pressure ◽  
Low Frequency ◽  
Internal Tides ◽  
Wind Component ◽  
Barrier Reef ◽  
Longshore Current ◽  
Shelf Waves

Winds and atmospheric pressure, sea level and water currents were measured at several locations over the continental shelf, both east and west of the Great Barrier Reef, between 14.5�s. and 20�S., from June to November 1980. The dominant wind direction changed from westward over the Coral Sea to north- westward (roughly parallel to the shore) over the shelf. A strong non-tidal low-frequency signal in all sea- level and longshore current data was found, highly coherent from site to site and strongly correlated with the longshore wind component over the shelf, though not with the atmospheric pressure. A model of wind- driven barotropic shelf waves is used to explain a number of observations, such as the invariance of temporal fluctuations of longshore current with distance from shore, and the northward longshore propagation of oceanic disturbances at a speed equal to twice that of the first-mode barotropic free shelf wave, a speed one order of magnitude smaller than that of the wind system. The low-frequency current fluctuations resulted in large water displacements, up and down the coast. Low-frequency cross-shelf currents were much weaker and less coherent. Two upwelling mechanisms are internal tides and internal Kelvin waves coupled to the barotropic shelf waves.

Upwelling by internal tides and kelvin waves at the continental shelf break on the Great Barrier Reef

1983 ◽  
Vol 34 (1) ◽  
pp. 65 ◽  
Author(s):  
E Wolanski ◽  
GL Pickard
Keyword(s):  
Continental Shelf ◽  
Great Barrier Reef ◽  
Low Frequency ◽  
Kelvin Waves ◽  
Shelf Break ◽  
Internal Tides ◽  
Wind Component ◽  
Barrier Reef ◽  
Tidal Period ◽  
Continental Shelf Break

A time series of 50 days duration was obtained of sea levels and winds and of temperature and currents at six depths from 27 to 104 m at 18�19'S.,147�21'E. on the continental shelf break between the Great Barrier Reef and the Coral Sea. The sea-level signal had a predominantly mixed solar and lunar semidiurnal tidal period. The currents consisted of a semidiurnal tidal component oriented primarily cross-shelf, except near the sea floor, superimposed on a low-frequency, predominantly longshore, southward component, coherent with depth, in geostrophic balance, and modulated by the longshore wind component Large fluctuations in temperature were observed, consisting of a low-frequency component, possibly generated by internal Kelvin waves, and iiucruarions of predominantiy solar semidiurnai iidai period. The latter fiiictuations are interpreted as evidence of internal tides of amplitude up to 110 m that may be generated by the interaction of the longshore currents with topographic irregularities in the shelf. It is suggested that, during any long-term studies of water properties near the shelf break, some additional monitoring of short-term temporal variations should be carried out to avoid data aliasing by internal tides. The bottom boundary layer appears to be very active in vertical mixing. Internal tides may be very important in introducing other water components, e.g. nutrients, to the outer Great Barrier Reef.

Stratification in a small lagoon in the Great Barrier Reef

1984 ◽  
Vol 35 (3) ◽  
pp. 273 ◽  
Author(s):  
JC Andrews ◽  
WC Dunlap ◽  
NF Bellamy
Keyword(s):  
Great Barrier Reef ◽  
Time Scales ◽  
Wind Stress ◽  
Thermal Stratification ◽  
Bottom Water ◽  
Reef Flat ◽  
Low Frequency ◽  
Wind Vector ◽  
Barrier Reef ◽  
Lunar Synchronization

Temperatures were measured in a small lagoon in the windward reef flat of Davies Reef in the central Great Barrier Reef and examined on three time scales to gain three perspectives on thermal stratification and the trapping of bottom water. Profiling for stratification and dye revealed layering where bottom water was trapped and released by the successive capping and uncapping of the lagoon by a diurnal thermocline. A 1-month monitoring array revealed a solar synchronization, with the temperature of reef-flat water exceeding temperatures of lagoon water by up to 1 5�C within 1 h of midday, and lagoon stratification lagging this by 1 h. There was also a lunar synchronization with mixing proceeding during nocturnal rising tides. Lagoon surface and bottom temperatures were also monitored for 11 months. The amplitude of the diurnal stratification showed no coherence either with the amplitude of the tide (marked spring-neap tides) or with scalar wind stress. The low frequency amplitude of the diurnal oscillation was coherent with the longshore wind vector at periods near 3 6 days and in a band approximately from 10 to 40 days. Daily stratification increased when winds were poleward and decreased when winds were equatonvard. Events of flushing were separated on average by 9 h, but the most frequently observed separation was 5 h and only 10% of separations exceeded 18 h during the 11 months.

scholarly journals Progressive seawater acidification on the Great Barrier Reef continental shelf

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Katharina E. Fabricius ◽  
Craig Neill ◽  
Erik Van Ooijen ◽  
Joy N. Smith ◽  
Bronte Tilbrook
Keyword(s):  
Coral Reefs ◽  
Continental Shelf ◽  
Great Barrier Reef ◽  
Ocean Acidification ◽  
Seawater Temperature ◽  
Barrier Reef ◽  
Saturation State ◽  
Seawater Acidification ◽  
Seawater Ph ◽  
Seawater Samples

Abstract Coral reefs are highly sensitive to ocean acidification due to rising atmospheric CO2 concentrations. We present 10 years of data (2009–2019) on the long-term trends and sources of variation in the carbon chemistry from two fixed stations in the Australian Great Barrier Reef. Data from the subtropical mid-shelf GBRWIS comprised 3-h instrument records, and those from the tropical coastal NRSYON were monthly seawater samples. Both stations recorded significant variation in seawater CO2 fugacity (fCO2), attributable to seasonal, daytime, temperature and salinity fluctuations. Superimposed over this variation, fCO2 progressively increased by > 2.0 ± 0.3 µatm year−1 at both stations. Seawater temperature and salinity also increased throughout the decade, whereas seawater pH and the saturation state of aragonite declined. The decadal upward fCO2 trend remained significant in temperature- and salinity-normalised data. Indeed, annual fCO2 minima are now higher than estimated fCO2 maxima in the early 1960s, with mean fCO2 now ~ 28% higher than 60 years ago. Our data indicate that carbonate dissolution from the seafloor is currently unable to buffer the Great Barrier Reef against ocean acidification. This is of great concern for the thousands of coral reefs and other diverse marine ecosystems located in this vast continental shelf system.

The Flatback Turtle, Chelonia depressa, in Queensland: Post-Nesting Migration and Feeling Ground Distribution

1983 ◽  
Vol 10 (3) ◽  
pp. 557 ◽  
Author(s):  
CJ Limpus ◽  
CJ Parmenter ◽  
V Baker ◽  
A Fleay
Keyword(s):  
Continental Shelf ◽  
Great Barrier Reef ◽  
Adult Female ◽  
Barrier Reef ◽  
Inshore Water ◽  
Eastern Australia ◽  
North Eastern ◽  
Nesting Beaches ◽  
Feeding Grounds

Between 1968 and 1981, a total of 813 adult female flatback turtles were tagged while nesting on Queensland beaches. Eight have been recovered at a distance, 216-1300 km north of their respective nesting beaches, in waters between the mainland and the Great Barrier Reef. The species' principal feeding grounds seem to be in turbid, shallow inshore water off north-eastern Australia and in the Gulf of Carpentaria; there are no records beyond the continental shelf.

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