Impact of atmospheric coastal jet off central Chile on sea surface temperature from satellite observations (2000–2007)

Abstract

[1] The coast of central Chile is characterized by intermittent low-level along-shore southerly wind periods, called coastal jets (CJs). In this study, we take advantage of long-term satellite data to document the CJs characteristics over 2000-2007 and investigate its impact on upwelling. The CJ structure has a core some 100 km from the shore and a cross-shore scale of $160 km, and it usually lasts for several days (3-10). Its period of occurrence ranges from weekly to a few months. On the basis of covariance analyses between wind stress and sea surface temperature (SST) anomalies, it is found that CJ activity is seasonally phase locked with SST, with a peak season in August-October. The statistically dominant forcing mechanisms of the SST cooling during CJ event is a combination of seaward advection of temperature resulting from Ekman transport, air-sea heat exchange, and Ekman-driven coastal divergence. However, case studies of two events suggest a significant sensitivity of the dominant upwelling forcing mechanisms to the background conditions. For instance, the upward Ekman pumping associated with cyclonic wind stress curl is enhanced for the event with the CJ located more to the south. Although there are limitations associated with both the formulation of the heat budget and the data sets, the results illustrate the complexity of the upwelling forcing mechanisms in this region and the need for realistic high-resolution forcing fluxes. A CJ activity index is also proposed that takes into account the coastal upwelling variability, which can be used for teleconnection studies.

Time-Space Variability of Chlorophyll-a and Associated Physical Variables within the Region off Central-Southern Chile

“…This band coincides with the transitional band of low variance in the Chl-a annual cycle described above ( Figure 5) and it is associated with the position of the coastal-CTZ jet, where WSC is close to zero (~75°W). In turn, this coincides with the climatological location of the low-level wind jet, which is characteristic in the region between 30 and 38°S [45,47]. On the other hand, the annual variance in sea level and EKE were mostly constrained to the CTZ, in agreement with the results of [10].…”

Natural and human-induced hypoxia and consequences for coastal areas: synthesis and future development

“…Hypoxia may result in the occurrence of denitrification in the water column (Naqvi et al, 2000 and2009). It has been suggested that, in addition to denitrification, anaerobic ammonium oxidation (e.g.…”

“…For example, the world's largest natural hypoxic zone that develops seasonally over the Western Indian continental shelf appears to have intensified over the last three decades (Naqvi et al, 2000 and2009). Given the huge increase in fertilizer consumptions in South Asia, this region is expected to receive large amounts of anthropogenic nutrient loadings through land runoff and atmospheric deposition (Seitzinger et al, 2002;Duce et al, 2008).…”

Seasonal variability of the Ekman transport and pumping in the upwelling system off central-northern Chile (∼ 30° S) based on a high-resolution atmospheric regional model (WRF)

“…Within central-northern Chile the area around 30 • S is characterized by the most intense upwelling favorable winds (Shaffer et al, 1999;Rutllant and Montecino, 2002). Additionally, local high-frequency forcing in the region is associated with atmospheric coastal jets with periods less than 25 days, which are related to synoptic dynamics of the mid-latitude pressure perturbations, in this case high pressures that migrate toward the east Rahn and Garreaud, 2013) and play a major role in coastal upwelling (Renault et al, 2009(Renault et al, , 2012Aguirre et al, 2012). All these features make the region a natural laboratory to explore the forcing mechanisms and describe the physical processes that modulate coastal upwelling.…”