scholarly journals Ocean Gliders Ride the Research Wave in the Agulhas Current

Eos ◽  
2018 ◽  
Vol 99 ◽  
Author(s):  
Marjolaine Krug ◽  
Sebastiaan Swart ◽  
Juliet Hermes
Keyword(s):  
South Africa ◽  
East Coast ◽  
Agulhas Current

Off the east coast of South Africa, robotic ocean gliders deployed in the Agulhas Current capture new data that help us better understand how energy dissipates in the ocean.

scholarly journals Seasonal and diurnal variation of lightning activity over southern Africa and correlation with European whistler observations

2006 ◽  
Vol 24 (2) ◽  
pp. 529-542 ◽  
Author(s):  
A. B. Collier ◽  
A. R. W. Hughes ◽  
J. Lichtenberger ◽  
P. Steinbach
Keyword(s):  
South Africa ◽  
Diurnal Variation ◽  
Southern Africa ◽  
Seasonal Variations ◽  
East Coast ◽  
Lightning Activity ◽  
Agulhas Current ◽  
Statistical Pattern ◽  
Seasonal And Diurnal Variation ◽  
Imaging Sensor

Abstract. Lightning Imaging Sensor (LIS) data have been analysed to ascertain the statistical pattern of lightning occurrence over southern Africa. The diurnal and seasonal variations are mapped in detail. The highest flash rates (107.2 km-2 y-1) occur close to the equator but maxima are also found over Madagascar (32.1 km-2 y-1) and South Africa (26.4 km-2 y-1). A feature of the statistics is a relatively steady contribution from over the ocean off the east coast of South Africa that appears to be associated with the Agulhas current. Lightning statistics are of intrinsic meteorological interest but they also relate to the occurrence of whistlers in the conjugate region. Whistler observations are made at Tihany, Hungary. Statistics reveal that the period of most frequent whistler occurrence does not correspond to the maximum in lightning activity in the conjugate region but is strongly influenced by ionospheric illumination and other factors. The whistler/flash ratio, R, shows remarkable variations during the year and has a peak that is narrowly confined to February and March.

Occurrence of tuna and mackerel larvae (Family: Scombridae) off the east coast of South Africa

2000 ◽  
Vol 51 (8) ◽  
pp. 777 ◽  
Author(s):  
Lynnath E. Beckley ◽  
Jeff M. Leis
Keyword(s):  
South Africa ◽  
East Coast ◽  
Temporal Distribution ◽  
Western Indian Ocean ◽  
Distribution Patterns ◽  
Agulhas Current ◽  
The North ◽  
Scomberomorus Commerson ◽  
Euthynnus Affinis ◽  
King Mackerel

Spatial and temporal distribution patterns of scombrid larvae along the east coast of South Africa were investigated from ichthyoplankton collections made during May–June 1990 (winter), October 1990 (spring) and February 1991 (summer). Results were analysed in relation to oceanographic conditions and known spawning localities of tuna and mackerels in the western Indian Ocean. In total, eight species were represented in the samples, with highest diversity in February and lowest numbers in May–June. Larvae of the temperate chub mackerel Scomber japonicus were most abundant at shelf stations during October. Larvae of neritic tunas Auxis sp. and Euthynnus affinis occurred in shelf stations off KwaZulu–Natal in February and extended southward in a plume along the shelf edge. Larvae of skipjack tunaKatsuwonus pelamis were most abundant in the Agulhas Current during February. Only a few larvae of oceanic tunas Thunnus spp., wahoo Acanthocybium solandri and king mackerel Scomberomorus commerson were collected in the Agulhas Current in the north of the study area during February when there was an intrusion of warm Tropical Surface Water. This indicates that spawning of these species probably does not occur off the east coast of South Africa.

Impact of Climate Change on the Agulhas Bank, South Africa ― a 100 year projection with consequences for the squid fishery

2020 ◽  
Author(s):  
Sarah Asdar ◽  
Michael J. Roberts ◽  
Zoe Jacobs ◽  
Ekaterina Popova
Keyword(s):  
Climate Change ◽  
South Africa ◽  
Water Retention ◽  
East Coast ◽  
Surface Current ◽  
Economic Importance ◽  
Economic Consequences ◽  
Local Circulation ◽  
Agulhas Current ◽  
Ocean Biogeochemistry

<p>The South and East coast of South Africa is strongly influenced by the warm, fast-flowing Agulhas Current. The Agulhas Bank, a shallow shelf on the southern tip of Southern Africa, is a crucial area for productivity which support fisheries of high economic importance for South Africa.  In this context of climate change, perturbations of this diverse, complex and highly variable marine environment could affect the productivity and lead to dramatic social and economic consequences for the region. To predict potential changes over the eastern and central Bank, we employ a high-resolution global coupled ocean-biogeochemistry model, NEMO-MEDUSA, simulated to year 2099. We find that even though the Agulhas Bank is warming over the next century, primary production does not experience a significant decrease. Additionally, we show that the Agulhas Current might shift its position, with intensification surface current velocity on the Bank hence reducing water retention over the Bank. This change in local circulation over the Bank could have a serious impact on the ecosystem of the region.</p>

scholarly journals TIDAL AND INERTIAL CURRENTS AROUND SOUTH AFRICA

1982 ◽  
Vol 1 (18) ◽  
pp. 155 ◽  
Author(s):  
E.H. Schumann ◽  
L.A. Perrins
Keyword(s):  
South Africa ◽  
Energy Spectrum ◽  
West Coast ◽  
Vertical Structure ◽  
East Coast ◽  
Coastal Ocean ◽  
Limited Information ◽  
The West ◽  
Agulhas Current ◽  
Inertial Currents

Limited information is available on currents in the semi-diurnal and diurnal frequency bands for the coastal ocean areas around Southern Africa. However, recently mooring data have become available from sites on the east, south and west coasts, and this paper analyses these results in an attempt to assess the importance of tidal and inertial currents. It is clear that on the narrow shelf on the east coast the Agulhas Current dominates the energy spectrum, and tidal currents should be relatively unimportant at such sites. In the south on the Agulhas Bank the Current is still important, but comparable energy resides in inertial and tidal fluctuations. Modal analysis indicates the tides are primarily barotropic, with the inertial fluctuations mainly baroclinic. In the absence of a major current on the west coast, most of the current variance occurs in the tidal and inertial bands; a complex vertical structure is also found. It is therefore clear that there are regions where such currents cannot be ignored.

BIOGENIC OPAL PRODUCTION IN THE AGULHAS CURRENT AND ITS CONNECTION TO ARIDIFICATION IN SOUTH AFRICA DURING THE MID-PLEISTOCENE

2018 ◽  
Author(s):  
Eduardo Ruiz Marin ◽  
◽  
Jason Coenen ◽  
Reed P. Scherer ◽  
Nathan D. Stansell ◽  
...  
Keyword(s):  
South Africa ◽  
Agulhas Current ◽  
Biogenic Opal

scholarly journals Population irruption of the clam Meretrix morphina in Lake St Lucia, South Africa

2017 ◽  
Vol 113 (7/8) ◽  
Author(s):  
Nelson A. F. Miranda ◽  
Nasreen Peer ◽  
Renzo Perissinotto ◽  
Nicola K. Carrasco ◽  
Salome Jones ◽  
...  
Keyword(s):  
South Africa ◽  
South African ◽  
East Coast ◽  
Severe Drought ◽  
Freshwater Input ◽  
Large Populations ◽  
Ocean Region ◽  
West Indian Ocean ◽  
First Time ◽  
Eastern Seaboard

The thick-shelled clam Meretrix morphina, previously referred to as Meretrix meretrix, now occurs in the west Indian Ocean region, along the eastern seaboard of Africa, from the Red Sea to the Mlalazi Estuary, close to the Tugela River. Its presence in South Africa is only of recent recording. Meretrix morphina was detected for the first time in Lake St Lucia in 2000. The population declined and was not detected from 2005 until 2011, most likely as a result of a severe drought that resulted in widespread desiccation and hypersalinity in the lake. The system then experienced increased freshwater input resulting in lower salinities from 2011 until 2014, during which time M. morphina reappeared and their population gradually increased. In 2015, M. morphina became abundant in St Lucia, attaining unprecedented densities of 447 ind./m2. Biomass, expressed as a fresh weight, varied in the different basins of St Lucia, ranging from 195 g/m2 at Lister’s Point to 1909.8 g/m2 at Catalina Bay. However, in 2016, when drought conditions returned, M. morphina disappeared. This species appears to thrive under brackish salinities and high temperatures. It is able to establish large populations with high biomass and can become dominant. However, M. morphina is sensitive to desiccation and hypersaline conditions. This clam has substantial commercial value and is exploited along the African east coast, particularly in Mozambique. In future, it may feature more prominently in South African estuaries. However, the ecology of M. morphina is still largely unknown.

Possible maternal offloading of metals in the plasma, uterine and capsule fluid of pregnant ragged-tooth sharks (Carcharias taurus) on the east coast of South Africa

2017 ◽  
Vol 24 (20) ◽  
pp. 16798-16805 ◽  
Author(s):  
Kristina Naidoo ◽  
Anil Chuturgoon ◽  
Geremy Cliff ◽  
Sanil Singh ◽  
Megan Ellis ◽  
...  
Keyword(s):  
South Africa ◽  
East Coast ◽  
Carcharias Taurus
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