Variability in hydroclimatic conditions observed during the period 2000-2009 in relation to the last decades, in the southeastern Bay of Biscay A. FONTÁN1, V. VALENCIA1, M. GONZÁLEZ1, J. SÁENZ2, Á. BORJA1 and G. ESNAOLA1 1AZTI-Tecnalia, Marine Research Division. Pasaia (Spain). E-mail: afontan@azti.es; www.azti.es 2Department of Applied Physics II, Fac. of Science and Technology, University of the Basque Country (Spain). I want to talk to you about Variability in hydroclimatic conditions during the 2000-2009 period in relation to the last decades, in the southeastern Bay of Biscay. December 18

Study area: southeastern Bay of Biscay OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS Study area: southeastern Bay of Biscay The study area is located in the southeastern Bay of Biscay. This area can be characterised as being more influenced by land climate and inputs than other open sea areas. However, series of oceanographic and meteorological data show similar trends to those observed in extensive oceanic areas. December 18 © AZTI-Tecnalia

EA+ EA- Cold Warm Wet Dry OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS The Eastern Atlantic (EA) is a very influential atmospheric pattern over the SE Bay of Biscay (Sáenz et al., 2001; Borja et al., 2008; Valencia et al., 2009). EA+ EA- L H Cold Wet Warm Dry Here, the Eastern Atlantic is a very important atmospheric pattern. It is characterised by three centres of activity: one located to the southwest of the Canary Islands, another near the Black Sea and a third west of Great Britain. The positive phase of the EA pattern is associated with warmer surface temperatures, together with below-average precipitation, in the study area. In contrast, the negative phase of the EA pattern is associated with below-average surface temperatures, together with above-average precipitation. December 18 © AZTI-Tecnalia

OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS The 2000-2009 decade: 2000 2009 highly coherent decade: EA - precipitation, temperature regime shift ~ 2007 ??? Throughout the last decade, several regime shifts and anomaly patterns for atmospheric and oceanic variability have been described, due to unusual values and persistent cumulative anomalies. In particular, the last decade is characterised by a positive phase of the EA in relation to warmer and drier climate. In contrast, a negative phase of the EA has dominated the circulation in the last 2 years with colder and wetter climate in comparison with the first period. So, the last decade can be characterised for being a highly coherent decade in terms of EA index, temperature and precipitation. December 18 © AZTI-Tecnalia

OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS To describe regime shifts in hydroclimatic conditions during the period 2000-2009, in relation to the last decades, in the SE Bay of Biscay. To apply the Kolmogorov-Zurbenko adaptive filter to identify regime shifts in time-series, induced by natural variability. In this context, the main aims of the present investigation are: To examine trends, anomaly patterns and regime shifts in hydroclimatic conditions during the decade 2000-2009, on a multidecadal context, in the SE Bay of Biscay. To apply the Kolmogorov-Zurbenko adaptive filter to identify regime shifts in time-series, induced by natural variability. December 18 © AZTI-Tecnalia Source: http://www.cpc.noaa.gov/

OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS Hydrographic data 1986-2001 The data used in this study are: Meteorological data (PP, T, EV,...) are from the Meteorological Observatory of San Sebastián of the Spanish meteorological Agency. Climatic indices are from the Climate Prediction Centre of the National Centre of Environmental Prediction. 25 years of Hydrological monthly data in the continental shelf up to 100 m from the Basque Government. SST daily data in the Basque coast from the Oceanographic Society of Gipuzkoa. Hydrological hourly data in the continental slope up to 200 m from the Basque meteorological agency. December 18 © AZTI-Tecnalia

Kolmogorov-Zurbenko adaptive filter (KZA): OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS Kolmogorov-Zurbenko adaptive filter (KZA): The KZA filter (Zurbenko, 1996) is a method for locating errors in long-term climatic time-series, caused by: erroneous acquisition techniques, changes in the instrumentation, etc. A NOVEL APPLICATION: detection of shifts in a time-series induced by natural variability. Iterative moving average filter. It adjusts the length of the moving average window according to the rate of change of the process. The criterion used to filter periods of less than T (Eskridge et al., 1997): T < q·√k where q=window size, k=nº iterations Moving average X(t) The KZA filter (Zurbenko, 1996) is a method for locating discontinuities in long-term climatic time-series, caused by: erroneous acquisition techniques, changes in the instrumentation, changes in the surroundings, etc. A novel application is utilised here: the filter is used for the detection of shifts in time-series induced by natural variability. The KZA Iterative moving average filter and it adjusts the length of the moving average window according to the rate of change of the process. It can be seen here the difference in locating discontinuities between a simple moving average filter and the KZA filter. KZA X(t) December 18 © AZTI-Tecnalia

Validation: Kolmogorov-Zurbenko adaptive filter (KZA): OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS Validation: Kolmogorov-Zurbenko adaptive filter (KZA): Regime shift in early 1990s with mild and dry winters in the NE Atlantic (Pérez et al., 1995, 2000; Valencia et al., 1996, 2003) For instance, the KZA can detect regime shift described by several authors. The KZA detects the regime shift observed in early 90s described by several authors. December 18 © AZTI-Tecnalia

Great Salinity Anomaly (Dickson et al., 1988) OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS Validation: Kolmogorov-Zurbenko adaptive filter (KZA): Great Salinity Anomaly (Dickson et al., 1988) Regime shift in early 90s + increased input of salty and warm waters to the S Bay of Biscay (Cabanas et al., 2003; Valencia et al., 2003) Also, it detects the great salinity anomaly in SST and so on. December 18 © AZTI-Tecnalia

2000-2009 in a multidecadal context: OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS 2000-2009 in a multidecadal context: A clear agreement between the EA index and the evaporation and air temperature is observed here for the whole period. In particular, for the last decade, the EA increases until 2003; this results in the increase of temperature and evaporation. Then, the EA index decreases with the subsequent decrease of temperature and evaporation. Again, the EA index increases in 2006 and subsequently it decreases. December 18 © AZTI-Tecnalia

2000-2009 in a multidecadal context: OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS 2000-2009 in a multidecadal context: An opposite trend between the temperature and precipitation is observed in the last decade. In general, a decrease of precipitation and an increase in temperature occurred until 2006 and then, the opposite pattern was observed. December 18 © AZTI-Tecnalia

Regime shifts in 2000-2009: EA index OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS Regime shifts in 2000-2009: EA index The positive phase of the EA index was particularly persistent during the 2000-2006 period, excluding 2004 and 2005 years. In 2007 a regime shift ocurred and the negative phase of the EA dominated the atmospherir circulation. December 18 © AZTI-Tecnalia

Regime shifts in 2000-2009: Precipitation OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS Regime shifts in 2000-2009: Precipitation In agreement with that observed for the EA index, the period 2000-2006 was characterised by low precipitations, whereas an increase in precipitation ocurred in 2007. December 18 © AZTI-Tecnalia

Regime shifts in 2000-2009: Air temperature OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS Regime shifts in 2000-2009: Air temperature Also, the period 2000-2006 was characterised by above-average temperatures, whereas a decrease in temperature ocurred in 2007 in agreement with the prevalence of the negative phase of the EA index from to 2007. Although the 2003 year was very warm, there is no a break here, which means that the filter not only detects the largest breaks but also the most persistent ones. Thus the high temperatures in 2003 were not persistent, whereas the lower temperatures from 2007 have remained until 2009. December 18 © AZTI-Tecnalia

Regime shifts in 2000-2009: River flow OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS Regime shifts in 2000-2009: River flow In general, a decresing trend in the river flow was observed until 2007, when an increase in the river flow ocurred. December 18 © AZTI-Tecnalia

Regime shifts in 2000-2009: Salinity upper 100 m OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS Regime shifts in 2000-2009: Salinity upper 100 m The reduced freshwater input resulted in an increase of salinity of the upper ocean in 2004. December 18 © AZTI-Tecnalia

Regime shifts in 2007-2009: Temperature and Salinity OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS Regime shifts in 2007-2009: Temperature and Salinity WARMER COLDER SALTIER LESS SALINE CTs-CTD chain at 10,20,30, 50,75, 100 and 200m The years that stand out from the last decade are 2003 and 2006 for being extremely warm. However, the period 2007-2009 appears to be relevant and deserves a separate analysis. Temperature and salinity hourly data in the upper 200m are available since 2007, in two offshore buoys located in the continental slope of the SE BoB. The cold temperatures, strong fresh water input in 2008 and the cyclone Klaus in January 2009 reduced heat content and salinity of the upper ocean in the SE BoB. December 18 © AZTI-Tecnalia

Regime shifts in 2007-2009: Salinity in the upper 200 m OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS Regime shifts in 2007-2009: Salinity in the upper 200 m Oct-2008 A decrease of salinity of the upper 200 m ocurred in October 2008 in relation to strong freshwater input. December 18 © AZTI-Tecnalia

Regime shifts in 2007-2009: Temperature in the upper 200 m OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS Regime shifts in 2007-2009: Temperature in the upper 200 m Jul-2008 Also a decrease in the heat content of the upper water column ocurred in July 2008 due to the prevalence of colder temperatures in the previous years. December 18 © AZTI-Tecnalia

OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS EA+ Q S 100m EA- PP Air T S 200m T 200m As a summary, The positive phase of the EA was dominant until 2007, with above average temperature and below average precipitaion in this period. In this period the freshwater inputs decrease resulting in a increase of the salinity in the upper water column. A regime shift ocurred in 2007 with the subsequent decrease of temperature and increase of precipitation. This resulted in a decrease of the heat content and salinity of the upper ocean. December 18 © AZTI-Tecnalia

The last decade can be dividided in 3 periods: OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS The KZA filter is precise for identifying regime shifts induced by natural varibility. Not only intensity of the breaks but also the persistence of the breaks within the window size is important. The last decade can be dividided in 3 periods: 2000-2003: warm and dry. 2004-2006: persistence of warm and dry climate resulted in an increase of upper ocean salinity. 2007-2009: transition to a colder and wetter period resulted in a reduction of upper ocean heat content and salinity. December 18 © AZTI-Tecnalia

VARIACIONES project (Basque Government) OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS VARIACIONES project (Basque Government) ESTIBB project (Spanish Government) ITSASEUS II project (Basque Government) La clorofila elemento clave (Basque Government) We would like to acknowledge all these institutions and financial support from different projects. December 18 © AZTI-Tecnalia

Thank you for your attention OVERVIEW – OBJECTIVES – DATA and METHODS – RESULTS – CONCLUSIONS – ACKNOWLEDGEMENTS Thank you for your attention December 18 © AZTI-Tecnalia