Coastal-Trapped Waves behind a Large Continental Shelf Island, Southern Great Barrier Reef

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.

Download Full-text

Progressive seawater acidification on the Great Barrier Reef continental shelf

Scientific Reports ◽

10.1038/s41598-020-75293-1 ◽

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.

Download Full-text

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

Marine and Freshwater Research ◽

10.1071/mf9830065 ◽

1983 ◽

Vol 34 (1) ◽

pp. 65 ◽

Cited By ~ 55

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.

Download Full-text

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

Wildlife Research ◽

10.1071/wr9830557 ◽

1983 ◽

Vol 10 (3) ◽

pp. 557 ◽

Cited By ~ 17

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.

Download Full-text