The Warming of the California Current:

1
The Warming of the California Current Dynamics,
Thermodynamics and Ecosystem Implications Arthur
J. Miller Scripps Institution of Oceanography,
UCSD NASA Oceanography PI Conference New
Orleans, LA June 5, 2003
2
The Warming of the California Current Dynamics,
Thermodynamics and Ecosystem implications Arthur
J. Miller Scripps Institution of Oceanography,
UCSD NASA Grant NAG5-9788 EOS
Interdisciplinary Science Program Ocean Carbon
Flux, Transport and Burial Within the Western
and Eastern U.S. Coastal Zones
Co-Investigators James C. McWilliams (IGPP,
UCLA) John R. Moisan (NASA/GSFC/Wallops) Dale
Haidvogel (Rutgers) Bruce Cornuelle (SIO,
UCSD) Keith Stolzenbach (UCLA)
3
The Warming of the California Current Dynamics,
Thermodynamics and Ecosystem implications Arthur
J. Miller Scripps Institution of Oceanography,
UCSD Co-authors Di Lorenzo, E., A. J.
Miller, N. Schneider, and J. C. McWilliams,
2003 Journal of Physical Oceanography, sub
judice.
4
Long-Term Physical Biological Dataset
California Cooperative Oceanic Fisheries
Investigation Hydrography
Southern California Coast and Baja
Temperature, Salinity and Zooplankton 1949 2003
seasonal data 20 m vertical resolution, from 0
500 m 70 - 80 km horizontal grid
CalCOFI historical sampling grid
5
Observations along the California Coast
6
Fundamental questions
California Current observations 1950-2000 1
ocean warming trend of 1.0 degree C 2 70
decline in zooplankton biomass What are the
physics that control the observed temperature
changes? Are these temperature changes linked to
global warming? Can we identify a clear
mechanism by which these physical changes impact
the ecosystem?
7
Limitations of the Observational Dataset
Satellite SST
Spatial and Temporal sampling aliasing
70 km
Very energetic Mesoscale variability
8
The Ocean Model
Satellite SST
Ocean Model SST
Example
70 km
Very energetic Mesoscale variability
Marchesiello and McWilliams, 2003
9
The Ocean Model Configuration
Regional Ocean Modeling System (ROMS) Primitive
Equations Horizontal Resolution 9 km Vertical
Resolution generalized sigma coordinate with 20
levels Open Boundaries North, West and
South Bathymetry ETOPO5 Sandwell and Smith
(TOPEX)
N
S. Francisco
California
E
W
m
Los Angeles
Latitude N
S
S. Diego
North Pacific Ocean
Longitude W
10
Local Atmospheric and Remote Oceanic Forcings
That Can Affect the Regional Oceanic Heat Budget
Mean Advection
Anomalous Advection
Southern California
Alongshore Wind Stress
11
Schematic of Oceanic Heat Budget Terms


Mean Advection
Local Surface Heat Fluxes
Upwelling
12
Schematic of Oceanic Heat Budget Terms


Mean Advection
Local Surface Heat Fluxes
Upwelling
Ocean Model Experiments
ww
Local Surface Heat Fluxes
Mean Advection
Upwelling
X
Exp 1
X
X
Exp 2
X
X
X
Exp 3
Q
Wind Stress
BC
13
Experimental Outline
1) Estimate the contribution of upwelling via
wind changes on long-term temperature
variations (Exp 1) 2) Estimate the contribution
of surface heat fluxes (Exp 2) 3) Estimate the
contribution of mean advection via boundary
condition changes (Exp 3) 4) Estimate impacts
on the ecosystem (Exp 3 with NPZD-type model)
14
Upwelling
EXP 1


Mean Advection
Local Surface Heat Fluxes
Upwelling
Ocean Model Experiments
Local Surface Heat Fluxes
Mean Advection
Upwelling
X
Exp 1
X
X
Exp 2
X
X
X
Exp 3
15
Alongshore Winds
EXP 1
16
Model Response to Wind Forcing ONLY
EXP 1
Temperature
Latitude N
C
EOF1 23
PC 1
1990
1970
1950
Longitude W
Model estimate Upwelling cooling of 1.0 C Net
cooling 1 C
17
Local Heat Fluxes
EXP 2


Mean Advection
Local Surface Heat Fluxes
Upwelling
Ocean Model Experiments
Local Surface Heat Fluxes
Mean Advection
Upwelling
X
Exp 1
X
X
Exp 2
X
X
X
Exp 3
18
Net Surface Heat Fluxes
EXP 2
Timeseries of surface net heat fluxesaveraged
over Southern California
Ocean is Cooling
Ocean is Heating
19
Model Response to Wind Forcing and Local Surface
Heat Fluxes ONLY
EXP 2
Temperature
Latitude N
C
EOF1 37
PC 1
1990
1970
1950
Longitude W
Model estimate Upwelling cooling of 1.0
C Surface Heat Fluxes warming of 0.5 C Net
cooling 0.5 C
20
Upwelling and Local Surface Heat Fluxes and Mean
Advection
EXP 3
Mean Advection
Alongshore Wind Stress
Southern California
21
Upwelling and Local Surface Heat Fluxes and Mean
Advection
EXP 3
Surface Heat Fluxes
Mean Advection
Alongshore Wind Stress
Southern California
22
Observed Surface Heat Fluxes EOF
EOF 1 58
PC 1
1
Canada
Heating
W m-2
US West Coast
Latitude N
0.5
CalCOFI
Model domain
Cooling
0
year
Longitude W
23
Local and Remote Heat Fluxes


Mean Advection
Local Surface Heat Fluxes
Upwelling
Ocean Model Experiments
Local Surface Heat Fluxes
Mean Advection
Upwelling
X
Exp 1
X
X
Exp 2
X
X
X
Exp 3
24
Model Response to Wind Forcing and Local Surface
Heat Fluxes and Mean Advection
EXP 3
Temperature
Latitude N
C
EOF1 32
PC 1
1990
1970
1950
Longitude W
Model heat budget estimates Upwelling cooling
of 1.0 C Surface Heat Fluxes warming of 0.5
C Mean Advection warming of 1.5 C Net warming
1 C
25
Impacts on the Ecosystem
10
Observed 20 m deepening of the isopycnals over
the last from 1950 -1998
m
0
-10
Thermocline Depth (estimated by the depth of
isopycnal 26.4)
Zooplankton Loge Tot. Vol.
7
6
5
4
1990
1970
1950
2000
1980
1960
26
The ocean model captures the observed thermocline
variations
Interannual and Decadal physical variations
CalCOFI Observed Thermocline
Thermocline depth over the last 50 years shows an
overall deepening of 20 meter.
10
0
m
-10
Model Thermocline
27
Schematic of Ecosystem Model
NO3
NH4
Phyto
Zoo
Chlorophyll-a
Small Detritus
Large Detritus
28
Biological response to the physical changes
Model Chl-a
10
Decline in CHL-A linked to thermocline deepening
in the model simulation. This is consistent with
the Zooplankton decline.
0
m
-10
Model Nutrocline
29
Summary
1) An increase in alongshore wind stress is found
to cool the California Current system by
intensifying coastal upwelling. The upwelling
contribution to the temperature trend is a
cooling up to 1.0 C. 2) The coastal warming
trend between 1950-1998 is associated with large
scale decadal variations in net surface heat
flux. The heat flux contribution to the
temperature trend is up to 2.0 C. Of this
warming 0.5 C is forced locally and 1.5 C is
advected by the mean currents. 3) The warming
trend between 1950-1998 is not obviously linked
to global warming because the variance of the
decadal variations in temperature (forced by heat
fluxes) is much larger than the expected trend
from global warming. Therefore the global warming
signature on this coastal environment has yet to
be clearly detected. 4) Model results suggest
that nutricline deepening associated with the
warming is responsible for the decline in
biological productivity by limiting the amount of
nutrients available to the ecosystem.
30
Continuing Research

• 1) Repeat with carbon cycle components and
  improved ecosystem.
• 2) California Current model hindcast of 1950-2003
  with assimilation of all data types for physical
  (hydrography, T/P SL, satellite SST) and
  biological (in situ NO3 and chl-a, SeaWiFS color)
  fields using ROMS adjoint models to adjust
  surface forcing fields and BCs.
• 2) Predictability of mesoscale eddies and
  ecosystem response using adjoint (4DVAR,
  representer and other) assimilation techniques
• 3) Real-time nowcasting and forecasting of
  California Current mesoscale variability and
  ecosystem response (www.sccoos.org).
• 4) California Current model runs forced by
  atmospheric forcing predicted by greenhouse-gas
  forced global coupled climate model forecasts.

Model/TOPEX sea level
Model/SeaWiFS chlorophyll-a
31

Modeling California Current System Dynamics and
Ecosystem Response
Emanuele Di Lorenzo, Art Miller, Bruce Cornuelle,
Doug Neilson (SIO) and John Moisan (NASA)
(0)
(1)
(2)
Satellite Observations
Model Hindcast
In Situ Observations
AVVISO TOPEX/ERS
CalCOFI 98-02
SSH
SSH
TOPEX
E2
E2
m
m
E1
E1
E1
SSH
Independent Validation
Data Assimilation
Independent Validation
?M N/m3
?M N/m3
SeaWiFS
E2
E2
Chl-a
Chl-a
E3
E3
E3
E1
E1
Chl-a