PREFACE-PIRATA-CLIVAR Tropical Atlantic Variability Conference UPMC, Paris, France November 28, 2016

Transcription

1 PREFACE-PIRATA-CLIVAR Tropical Atlantic Variability Conference UPMC, Paris, France November 28, 2016 Collaborative Research Center 754 SFB 754 Potential impact of Atlantic climate modes on the ventilation of the oxygen minimum zone in the eastern tropical north Atlantic Kristin Burmeister1 and Joke Lübbecke1,2 1 GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany Christian-Albrechts-Universität zu Kiel, Germany 2

2 Introduction: The oxygen minimum zone in the eastern tropical North Atlantic 23 W section Zonal velocity Oxygen Brandt et al. (2010) 2

3 Introduction: The oxygen minimum zone in the eastern tropical North Atlantic 23 W section Zonal velocity Main oxygen supply for OMZ by and Oxygen (Stramma et al., 2008a) Brandt et al. (2010) 2

4 Introduction: The oxygen minimum zone in the eastern tropical North Atlantic Oxygen variability N, W Mooring observations along 23 W µmol/kg Stramma et al. (2008b) Brandt et al. (2015) Norm. power spectral density of O2 at m, N, W Model simulation 3

5 Introduction: The oxygen minimum zone in the eastern tropical North Atlantic Oxygen variability N, W Mooring observations along 23 W µmol/kg Long-term trend modulated by variability on various Stramma et al. (2010) time scales Brandt et al. (2015) Norm. power spectral density of O2 at m, N, W Model simulation 3

6 Introduction: The Atlantic zonal and meridional mode Atlantic zonal mode (AZM) Atlantic meridional mode (AMM) NOAA SST 1. EOF 20 N 10 N 0 NOAA SST 2. EOF 20 N N 0 10 S S S S 50 W 30 W 10 W 10 E Peaks in June to August Interannual time scale Mainly governed by ocean dynamics W 30 W 10 W 10 E -0.6 Peaks in March to May Decadal time scale Mainly governed by thermodynamics 4

7 Introduction: The Atlantic zonal and meridional mode Atlantic zonal mode (AZM) Atlantic meridional mode (AMM) NOAA SST 1. EOF 20 N 10 N 0 10 S NOAA SST 2. EOF 20 N N Link between NECC variability and Atlantic climate modes 10 S S S 50 W 30 W 10 W 10 E Peaks in June to August Interannual time scale Mainly governed by ocean dynamics (Hormann et al., 2012) 50 W 30 W 10 W 10 E -0.6 Peaks in March to May Decadal time scale Mainly governed by thermodynamics 4

8 Introduction: The Atlantic zonal and meridional mode Atlantic zonal mode (AZM) Atlantic meridional mode (AMM) NOAA SST 1. EOF 20 N 10 N 0 10 S NOAA SST 2. EOF 20 N N S Do the Atlantic climate modes impact the ventilation of the oxgen minimum zone? S S 50 W 30 W 10 W 10 E Peaks in June to August Interannual time scale Mainly governed by ocean dynamics W 30 W 10 W 10 E -0.6 Peaks in May to March Decadal time scale Mainly governed by thermodynamics 4

9 Data: Model simulations Oxygen in m µmol/l Contours: O2 in µmol/l of World Ocean Atlas Zonal velocity at 0, m/s Biogeochemical model coupled with high resolution (1/10 ) nested OGCM TRATL01 from 1958 to 2007 (Duteil et al., 2014) in combination with Black contours: O2 in µmol/l Red countour: 27.0 kg/m3 isopycnals Observational data (ship sections, moorings, satellite data) Reanalysis data (NOAA, GODAS, SODA, ORAS4) Duteil et al. (2014) 5

10 Results: Indices of the Atlantic climate modes ATL3 AMM 6

11 Results: Composites AZM Oxygen and zonal velocity at m Positve minus negative AZM events Total mean Black contours: O2 in µmol/l 7

12 Results: Composites AZM Oxygen and zonal velocity at m Positve minus negative AZM events Total mean Black contours: O2 in µmol/l Stronger eastward flow at 4 N during positive AZM events compared to negative AZM events 7

13 Results: Composites AZM Oxygen and zonal velocity at m Positve minus negative AZM events 8

14 Results: Composites AZM Oxygen and zonal velocity at m Positve minus negative AZM events Positive velocity anomalies associated with positive oxygen anomalies and vice versa 8

15 Results: Composites AMM Oxygen and zonal velocity at m Positve minus negative AMM events Total mean Black contours: O2 in µmol/l 9

16 Results: Composites AMM Oxygen and zonal velocity at m Positve minus negative AMM events Total mean Black contours: O2 in µmol/l Northward shift of eastward flow at 4 N during negative AMM events compared to positive AMM events 9

17 Results: Composites AMM Oxygen and zonal velocity at m Positve minus negative AMM events 10

18 Results: Composites AMM Oxygen and zonal velocity at m Positve minus negative AMM events Negative velocity anomalies associated with negative oxygen anomalies and vice versa 10

19 Conclusion and Outlook The oxygen minimum zone in the eastern tropical North Atlantic Link between oxygen and zonal current variability partly modulated by the Atlantic zonal and meridional mode Outlook Compare to observational and reanalysis data Estimate core position and intensity of zonal current bands according to Johnson et al. (2002) and Hsin and Qiu (2012) Extend model simulation until

20 Results: Indices of the Atlantic climate modes ATL3 AMM 12