CalCOFI – The 2014/15 Warm Anomaly
The 2014/15 Warm Anomaly in the
Southern California Current
Ralf Goericke & CalCOFI Tech. Group
Scripps Inst. of Oceanography
La Jolla, May 2015
CalCOFI 1984 to 2015
New Horizon, LOA 52 m
David Star Jordan, LOA 52 m
Cruises: four times a year covering the above 75 station pattern during summer &
fall or a 113 station pattern during winter and spring.
Offshore Stations since 1984: 66 Stations,
Nearshore Stations since 2004: 9 Stations,
~ 2 to 400 km from shore, depth 50 to 4000m
~ 2 to 10 km from shore, depth ~20 m
Average Hydrography
10 m Temperature
10 m Salinity
10 m Nitrate
10 m Chlorophyll a
1984 to 2014 Distributions of 10 m Temperature, Salinity, Nitrate and Chl a.
Anomalies Jan 2015 at 10 m
Temperature
1010
mm
Temp
(StAnom.)
m Salinity
10 m 10
Salinity
(StAnom.)
m Nitrate
10 m 10
Nitrate
(StAnom.)
Chlorophyll
a
1010mmChl
a (StAnom.)
January 2015, 10 m Depth Anomalies: Temperature, Salinity, Nitrate and Chl a.
2014/15 Temp Anomalies at 10 m
April 2014 - 10 m Temp StAnom
July 2014 - 10 m Temp StAnom
Nov 2014 - 10 m Temp StAnom
Jan 2015 - 10 m Temp StAnom
The 2015 Warm Anomaly has intensified
TS Diagrams – Annual Averages
California Current South
(Lines 87 - 93 Stations 60 - 90 )
California Current North
(Lines 77 - 83 Stations 70 - 90 )
17
Depths: 0, 10, 20, 30 m
Temperature (?C)
15
13
11
9
2014
2013
2012
7
2011
1984 - 2014
5
32.8
33.3
33.8
Salinity
34.3
32.8
33.3
33.8
34.3
Salinity
TS Changes: In the north only a strong warming of the surface
layer; in the south the same plus a decrease in spiciness at depth.
Chlorophyll – Annual Averages
Chl a vs. Depth for the CalCOFI region and the northern coastal and southern Calif. Current areas.
Coastal North
Calf. Current South
0
20
20
20
40
40
40
60
60
60
80
2014
100
2013
120
Depth (m)
0
Depth (m)
Depth (m)
CalCOFI Domain
0
80
100
80
100
120
120
140
140
160
160
180
180
2012
140
2011
160
1984 - 2014
180
0.0
0.3
0.6
0.9
1.2
0.0
1.0
2.0
3.0
4.0
Chlorophyll a (μg L-1)
0.0
0.1
0.2
0.3
0.4
0.5
Surface layer phytoplankton biomass has decreased by a
factor of two or more depending on region.
Phytoplankton and Nutrients
3
4
A - ML Temp Anom.
3
Anomaly (m) .
Anomaly (?C) .
2
1
0
-1
1
0
-2
2
B - Nitracline Depth
Chl a Anomaly (ug L-1) .
20
Anomaly (m) .
2
-1
-2
30
C - ML Nitrate Anom.
10
0
-10
-20
D - ML Chl Anom.
1
0
-1
-2
-30
1984
1988
1992
1996
2000
2004
2008
2012
2016
1984
1988
1992
1996
2000
2004
2008
2012
2016
Phytoplankton biomass was controlled by the availability of inorganic nitrogen
What is the Context? What are the Drivers?
Questions:
• Winds and upwelling
• Comparison to the 1998/99 ENSO event
• Changes on isopycnals
Upwelling at 33 and 36 °N
2014
2015
36°N – Central Calf.
2014
2015
33 °N – South Cal. Bight
Coastal upwelling in the S. Calif. Current was not anomalous
during the 2014 and 2015 cruises (except for July 2014)
10 m and 100 m Temp over Time
Temp StAnom at 10 m – Line 90
Temp StAnom at 100 m – Line 90
The 2014/15 Warm Anomaly is confined to the Surface Layer!
At the surface its magnitude is similar to the 1998 El Nino.
At depth (100 m) the 2014/15 Warm Anomaly is barely expressed.
Stratification along Line 90
Line 90 stratification (N2) anomalies
(averaged from 10 to 200 m)
2.0
1.0
-5
-2
Anomaly (10 cycles sec )
3.0
0.0
-1.0
-2.0
1984
1987
1991
1995
1999
2003
2007
2011
2015
Upper ocean stratification during the warm anomaly was the
strongest observed since 1984
Properties at Depth - Anomalies
Depth (avg. ~ 127 m)
Nitrate (average ~ 21 uM)
2.0
20
Anomaly (uM)
Anomaly (m)
40
0
-20
-40
-60
-1.0
0.1
1984 1988 1992 1996 2000 2004 2008 2012 2016
Anomaly (molar)
Anomaly (kg m3)
0.0
-2.0
1984 1988 1992 1996 2000 2004 2008 2012 2016
0.1
0.0
-0.1
-0.1
-0.2
1.0
N-P Ratio (average ~ 12.7)
0.5
0.0
-0.5
Spiciness (avg. ~ 0.09)
-0.2
1984 1988 1992 1996 2000 2004 2008 2012 2016
-1.0
1984 1988 1992 1996 2000 2004 2008 2012 2016
At depth, no property changes were observed on isopycnals (shown is σt = 26.0).
However, the depth of the isopycnal changed significantly!
CalCOFI – The 2014/15 Warm Anomaly
Summary:
• The warm anomaly is strongly expressed at the surface, with effects
similar to those observed during the 1998 El Nino.
• The anomaly has only had weak effects on properties at depth (100
to 400 m).
• Increased stratification caused decreased fluxes of nitrate into the
euphotic zone, limiting phytoplankton biomass.
• Phytoplankton biomass was reduced by up to a factor of two in some
regions.
CalCOFI – The 2014/15 Warm Anomaly
Thank You !