You searched for subject:(Angola Current). Showing records 1 – 2 of 2 total matches.
1. Li, Pin. Quantifying the Contribution of Mean Flow and Eddy Advection to the Warm SST Bias in the Southeast Tropical Atlantic Region.
Degree: PhD, Oceanography, 2018, Texas A&M University
In current-generation climate models, the warm sea surface temperature (SST) bias problem is most commonly seen in the eastern boundary upwelling systems (EBUSs), and is most pronounced and most prevalent in the Southeast Tropical Atlantic (SETA) region. Previous studies have shown that the coastal wind pattern in this region, namely the Benguela low-level coastal jet (BLLCJ), is of great importance for the generation of such SST bias, because the coastal ocean circulation is highly sensitive to the off-shore structure of the wind forcing. Using an eddy-resolving regional ocean model, we first show that the SST bias in the region is drastically reduced when forced with simulated winds from a high-resolution regional atmospheric model. We subsequently demonstrate that the SST bias is highly sensitive to the spatial structure of the wind stress curl (WSC). We also find that when the ocean model is forced by a realistic high-resolution wind, the ocean model resolution is of second order importance in reducing the SST bias. Furthermore, we use a double-time average (DTA) method to quantify the contribution of heat budget terms, and show that the horizontal advection contributes significantly to the SST bias. We then examined the question: To what extent do ocean eddies play a role in balancing the coastal ocean heat budget and affecting the SST bias? By experimenting with a submesoscale eddy-permitting regional ocean model, we show that ocean eddies in the Southeast Tropical Atlantic region are most energetic near the Angola-Benguela Front (ABF), the Lüderitz Upwelling Cell region and the Agulhas Leakage region. In these three regions, comparisons between the two model simulations forced with the low- vs high-resolution winds suggest that the SST bias is mainly generated by mean flow advection with ocean eddies playing the role of counteracting the warming induced by the mean flow advection in this region. Advisors/Committee Members: Chang, Ping (advisor), Lin, Xiaopei (committee member), Hetland, Robert (committee member), Stössel, Achim (committee member), Saravanan, Ramalingam (committee member).
Subjects/Keywords: Climate model; SST bias; southeast tropical Atlantic; Benguela low-level coastal jet; Angola Current; Benguela Current; upwelling; eddy advection
Li, P. (2018). Quantifying the Contribution of Mean Flow and Eddy Advection to the Warm SST Bias in the Southeast Tropical Atlantic Region . (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/174045
Li, Pin. "Quantifying the Contribution of Mean Flow and Eddy Advection to the Warm SST Bias in the Southeast Tropical Atlantic Region." 2018. Doctoral Dissertation, Texas A&M University. Accessed January 18, 2021. http://hdl.handle.net/1969.1/174045.
Li, Pin. "Quantifying the Contribution of Mean Flow and Eddy Advection to the Warm SST Bias in the Southeast Tropical Atlantic Region." 2018. Web. 18 Jan 2021.
Li P. Quantifying the Contribution of Mean Flow and Eddy Advection to the Warm SST Bias in the Southeast Tropical Atlantic Region. [Internet] [Doctoral dissertation]. Texas A&M University; 2018. [cited 2021 Jan 18]. Available from: http://hdl.handle.net/1969.1/174045.
Li P. Quantifying the Contribution of Mean Flow and Eddy Advection to the Warm SST Bias in the Southeast Tropical Atlantic Region. [Doctoral Dissertation]. Texas A&M University; 2018. Available from: http://hdl.handle.net/1969.1/174045
2. Winkler, Alexander Claus. Using a multi-method approach to understand the movement patterns and the associated environmental correlates of an iconic West African recreational fish.
Degree: Faculty of Science, Ichthyology and Fisheries Science, 2019, Rhodes University
The leerfish (Lichia amia), is a large, primarily coastal recreational fish species with a distribution extending from Portugal down the west coast of African to southern Mozambique. Owing to its large size (30 kg), strong fighting abilities and habit of taking surface artificial lures, this species has taken on an iconic stature among shore-based recreational anglers. Its reputation has made it an important angling tourism species that makes an important contribution to the economy of developing countries. For example, the species brought US$243 per harvested kilogramme into the local southern Angola economy. Despite its high value, little is known about its movement patterns in the northern Benguela coastal region, a region which includes southern Angola and northern Namibia. While much is known about the migratory patterns of the South African stock of L. amia, recent molecular studies have shown that the northern Benguela stock of L. amia has been isolated from the South African population for at least two million years, a consequence of the development of the cold Lüderitz upwelling cell in southern Namibia. Although the global population of L. amia is considered a single species, prominent biogeographic barriers within its distribution and subtle morphological differences between specimens captured within its tropical versus warm-temperate distribution suggest otherwise. A multi-method approach incorporating passive acoustic telemetry (PAT), recreational catch-per-unit-effort (CPUE) and conventional tagging (CT) in southern Angola, as well as recreational fisher-ecological knowledge (FEK) from Namibia, was used to investigate the large-scale movement patterns of L. amia within the northern Benguela coastal region. While each method had its own associated limitations, the combination provided a holistic picture of the population's seasonal migratory patterns. Furthermore, PAT successfully identified partial migration with 25% vs 75% of monitored fish exhibiting resident (movements < 100 km) or migratory (movements > 100 km) behaviour, respectively. Further behavioural diversity was observed with 'resident', 'roaming' and 'embayment' contingents identified based on varying levels of affinity to certain habitats. The presence of both resident and migratory individuals within the northernmost study during June and July, combined with available biological information, suggested that area-specific spawning may take place. While PAT, CPUE and CT largely aligned in determining area specific high-area use, results from network analyses and mixed effects models conducted on the PAT data supported the spawning hypothesis, with anomalous behaviour around specific receivers during the spawning season. All fish, regardless of behavioural contingent, displayed similar movement behaviour during the spawning season and this was driven by factors generally associated with reproduction, such as lunar illumination. Interestingly, these drivers were different from those that determined the area specific use of individuals outside…
Subjects/Keywords: Carangidae fishing; Carangidae – Migration; Carangidae – Namibia; Carangidae – Angola; Fish tagging; Carangidae – Benguela Current; Underwater acoustic telemetry; Ocean temperature – Physiological effect; Fishes – Effect of temperature on
Winkler, A. C. (2019). Using a multi-method approach to understand the movement patterns and the associated environmental correlates of an iconic West African recreational fish . (Thesis). Rhodes University. Retrieved from http://hdl.handle.net/10962/76530
Winkler, Alexander Claus. "Using a multi-method approach to understand the movement patterns and the associated environmental correlates of an iconic West African recreational fish." 2019. Thesis, Rhodes University. Accessed January 18, 2021. http://hdl.handle.net/10962/76530.
Winkler, Alexander Claus. "Using a multi-method approach to understand the movement patterns and the associated environmental correlates of an iconic West African recreational fish." 2019. Web. 18 Jan 2021.
Winkler AC. Using a multi-method approach to understand the movement patterns and the associated environmental correlates of an iconic West African recreational fish. [Internet] [Thesis]. Rhodes University; 2019. [cited 2021 Jan 18]. Available from: http://hdl.handle.net/10962/76530.
Winkler AC. Using a multi-method approach to understand the movement patterns and the associated environmental correlates of an iconic West African recreational fish. [Thesis]. Rhodes University; 2019. Available from: http://hdl.handle.net/10962/76530