Trends of ocean-bay connectivity
Mélanie Raimonet, Jim Cloern, Tara Schraga,
Anthony Malkassian, Alan Jassby, Emily Novick, David Senn
Delta-Bay Science Conference – Sacramento
October 29th, 2014
OCEAN
Central Bay
South Bay
California coastal upwelling
Source: wikipedia
coastal upwelling
COLD & NUTRIENT-RICH WATERS
Source: Ryan et al. (2005) Cold waters
(and nutrient-rich) Phytoplankton
Two indicators of upwelling activity
TEMPERATURE CHLOROPHYLL
San Francisco Bay
Questions
Is there a signal of oceanic change over time?
How does this oceanic signal propagate into the Bay?
o Central Bay
o South Bay
Daily Upwelling Index 1967-2013 (Bakun, 1973; Schwing et al., 1996)
based on surface atmospheric pressure fields amount of water upwelled (m3/s/100m of coastline)
Source: NOAA/NMFS/PFEG
Daily average of 36 and 39°N
Methods
San Francisco Bay
36
39
Cumulative Upwelling Index (CUI)
STI
Spring Transition Index (days)
Total Upwelling Magnitude Index (m3/s/100m of coastline)
Source: Bograd et al. (2009)
TUMI
Days since 1st January
Monthly: Garcia-Reyes et al. (2014) Satellite images Kahru et al. (2012) 1997-2013
Temperature Chlorophyll
Farallon islands
San Francisco Bay
Weekly/monthly sampling Bottom/surface USGS dataset 1984-2013
Daily surface water sampling Farallon shore station 1991-2013
1985 2015 1995 2005
Investigating trends Time series
Tem
per
atu
re (
°C)
Annual trend for each month over a time period (e.g. 1984-2013)
statistically significant
Trend for each month
Tren
d (
°C/y
r)
Month
1 2 3 4 5 6 7 8 9 10 11 12
wq R package (Jassby and Cloern, 2014)
Is there a signal of oceanic change over time?
Stronger and earlier upwelling since 1999 Temperature decrease and chlorophyll increase?
Spring Transition Index
Total Upwelling Magnitude Index
PDO-
NPGO+
Chenillat et al. (2012)
Ch
loro
ph
yll t
ren
d (
µg
/l/y
r)
Trends at Farallon islands
Temperature Chlorophyll
decrease
increase
significant significant
Tem
per
atu
re t
ren
d (
°C/y
r)
How does this oceanic signal propagate into Central Bay?
Similar cooling trend significant in March, but less strong
Central Bay (bottom) Farallon (surface)
Temperature trends in Central Bay
-2 to -2.6°C in 22 years -1°C in 22 years
significant
Tem
per
atu
re t
ren
d (
°C/y
r)
common trend
Same significant increase at both sites: May & October
Chlorophyll trends In Central Bay
Central Bay (surface) Farallon (surface)
significant
Ch
loro
ph
yll t
ren
d (
µg
/l/y
r)
common trend
Central Bay versus Farallon datasets
Temperature Chlorophyll
Significant correlations between Central Bay and Farallon for both temperature and chlorophyll
(µg
/l)
cor=0.66 p<0.001
cor=0.41 p<0.001
Annual mean surface chlorophyll in Central Bay
1.0
0.8
0.6 .t::. (.)
-0 <ll N 0.4 ro E '-0
0.2 z
0.0
1985 1990 1995 2000 2005 2010
Spearman rho=0.52 p<0.01
Surface Chl in Central Bay significantly correlated with TUMI
Annual mean surface chlorophyll in Central Bay
How does this oceanic signal propagate into South Bay?
South Bay
Tem
per
atu
re t
ren
d (
°C/y
r)
Temperature decrease in April in SB => 1 month lag with CB
Central Bay
Temperature
Bottom water 1991-2013
Ch
loro
ph
yll t
ren
d (
µg
/l/y
r) Central Bay
Surface water 1991-2013
Chlorophyll
Chl increase in May/Jun/Oct like CB, but also until Dec
South Bay
common trend
Other factors e.g. lower grazing after 1999
Cloern et al. (2007)
Take home messages
• Stronger and earlier upwelling since 1999
• Colder temperature and higher chlorophyll in Farallon
• Colder temperature propagates into Central and South Bay
• Higher chlorophyll in the Central and South Bay too (due to upwelling and other factors e.g. grazing, turbidity…)
We cannot forget that the ocean is influenced by climate and that the Bay is influenced by the ocean!
To manage water quality and determine baselines:
Thank you for your attention
Special thanks to: Marisol Garcia-Reyes, John Largier, Raphael Kudela, Fanny Chenillat, Emmanuele DiLorenzo
