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Title

Variabilidade climática e tendencias decadais nos forzamentos meteorolóxicos e as propiedades das augas adxacentes a Galicia

AuthorsRuiz-Villarreal, M.; Álvarez-Salgado, Xosé Antón ; Cabanas, J. M.; Pérez, Fiz F. ; Castro, Carmen G. ; Herrera, José Luis ; Piedracoba, Silvia ; Rosón, Gabriel
Issue Date2009
PublisherXunta de Galicia
CitationEvidencias e impactos do cambio climático en Galicia: 271-286 (2009)
Abstract[EN] In this chapter, trends in the longest available series of oceanographic variables on the Galician coast are analysed. Sea surface temperature and air temperature over the sea were obtained from the ICOADS project, which compiled observations on board opportunity ships from the end of the 18th century. These temperatures increased at a rate of about a tenth of degree per decade. The increase is larger and more significant in sea surface temperature than in air temperature over the sea and is comparable to the trend obtained in the average global temperature. Variability observed in temperature is correlated with variability in the atmospheric forcing of the Atlantic Ocean described by the teleconnection index NAO (North Atlantic Oscillation) and with the interdecadal oscillation that has been described in the entire Atlantic Ocean basin (AMO, Atlantic Multidecadal Oscillation pattern). Since cycles of upwelling-downwelling are fundamental for the dynamics of coastal circulation in Galicia, the trend in upwelling-favourable winds was studied. The upwelling index series calculated from geostrophic winds at 43º N 11ºW shows a tendency of reduction of upwelling in the last decades (from 1966), especially evident in a seasonal analysis. This trend is also apparent in surface winds obtained from COADS project. A time series of temperature and salinity of subsurface waters near the Galician coast was constructed and waters in the 27.1 isopycnal, close to the thermocline, were analysed. No significant linear trend was observed, but interannual and decadal variability were evident, with an alternation of periods of warmer and saltier waters with periods of less saline waters. Taking the 80s as the origin for analysis of trends would lead to the conclusion that temperature and salinity of these waters have increased, but the inspection of the entire series reveals that variability is more complex. The change in trend in oceanic and atmospheric circulation patterns over the Atlantic observed in the 70s needs to be taken into account in any analysis of climatic trends in the Atlantic and especially in waters adjacent to Galicia
[GA] Neste capítulo analízanse as tendencias obtidas nas series máis longas dispoñibles de variables oceanográficas nas costas galegas. A temperatura superficial do mar e do aire sobre o mar obtivéronse do proxecto ICOADS , que recompilou observacións feitas a bordo de barcos desde finais do século XVIII. A temperatura superficial do aire sobre o mar e a do mar aumentaron a unha taxa de arredor dunha décima de grao por década. O aumento resulta un pouco maior e máis significativo na temperatura do mar que na do aire, e é comparable ao obtido na temperatura media do globo. A variabilidade observada na temperatura está correlacionada coa variabilidade no forzamento atmosférico no Atlántico descrita co patrón de teleconexión NAO (North Atlantic Oscillation, oscilación do atlántico norte) e coa oscilación interdecadal descrita en todo o Atlántico (patrón AMO, oscilación atlántica multidecadal). Dado que os ciclos de afloramento-afundimento son fundamentais na dinámica da circulación costeira en Galicia, analizouse a tendencia nos ventos favorables ao afloramento. A serie de índice de afloramento calculada de ventos xeostróficos en 43º N 11º W mostra unha tendencia de redución do afloramento nas últimas décadas (desde 1966), especialmente evidente nunha análise estacional. Esta tendencia tamén é apreciable nos ventos en superficie do mar obtidos do proxecto COADS . Construíse unha serie temporal de temperatura e salinidade nas augas subsuperficiais na costa adxacente a Galicia e analizáronse as augas da isopicna 27.1, preto da termoclina. Non se observou unha tendencia lineal significativa, pero si variabilidade interanual e decadal, cunha alternancia de períodos de augas máis salinas e quentes con outros de augas menos salinas. Se se toma como orixe na análise de tendencias a década dos oitenta, a conclusión sería que a temperatura e a salinidade destas augas aumentou, pero a inspección da serie completa revela que a variabilidade é máis complexa. O cambio de tendencia na década dos setenta nos patróns de circulación atmosférica e oceánica no Atlántico debe ser tido en consideración en calquera análise de tendencias climáticas no Atlántico e concretamente nas augas adxacentes a Galicia
Description19 páginas, 8 figuras
Publisher version (URL)http://siam.cmati.xunta.es/resultados-do-proxecto
URIhttp://hdl.handle.net/10261/110602
ISBN978-84-453-4782-9
Appears in Collections:(IIM) Libros y partes de libros
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