Transcript Mantua guest lecture.. - University of Washington

Northwest Climate and Puget
Sound
Nate Mantua
Aquatic and Fishery Sciences
and Climate Impacts Group
University of Washington
Winter winds
and pressure over
the North Pacific
Summer winds
and pressure over
the North Pacific
L
L
H
H
“Aleutian Low”
“Subtropical High”
Runoff patterns are temperature and
elevation dependent
Puget Sound Precip
Oct
Feb
Skagit
Jun
Oct
Feb
Jun
Puyallup
Oct
Feb
Jun
Skokomish
Oct
Feb
Jun
Monthly mean
river discharge
1993-2002
• Total runoff into Puget
Sound peaks in
winter and May-June
• In contrast, the Fraser
River has minimum
discharge in winter,
peaks in May-JuneJuly
4
Coastal upwelling
• Spring and
summer winds
from the north
cause
upwelling of
cold, nutrient
rich waters into
the coastal
waters of the
western US
Climate variability and Puget Sound
TIMESCALE &
PREDICTABILITY
Puget Sound
Oceanography
“Weather”
ENSO
PDO
Global Warming
• Days to Weeks
• Years
• Decades
• Centuries?
• < 2 Weeks
• 1 Year
• 2 Years
• Decades?
Fickle winds can cause large changes in
upwelling habitat on short time-space scales
Stonewall Banks Buoy SST
June 18 - August 2 2005
17.5C on July 14
~11C on July 20
June
July
August
Buoy SST plot courtesy of Pete Lawson
20 July 2005 SST
NOAA CoastWatch image
El Niño Impacts
on the
northeastern
Pacific Ocean
Sept 1997 El Niño
An intense Aleutian Low
pressure cell in fall and winter
brings warm southerly winds to
our region, making for a mild
winter and strong coastal
downwelling that warms and
stratifies the coastal ocean.
Year-to-Year changes associated with ENSO variations
can also be large -- note the 3 to 4ºC (5 to 7ºF) decline in
coastal SSTs between Septembers of 1998 and 1999
Sept 1997 El Niño
Sept 1998 La Niña
17
18
15
13
14
12
Observed SST anomalies
Jan 16-Feb 12 2011
• Last summer coastal
ocean and Puget
Sound surface
temperatures were
running cool … at
least for coastal
waters, the key factor
was intense north
(upwelling) winds
Pacific Decadal
Oscillation
El Niño/Southern
Oscillation
20-30 years
6-18 months
North Pacific
Equatorial Pacific
Warm phase
PDO
ENSO (El Niño)
Source: Climate Impacts Group, University of Washington
Race Rocks as an indicator site for
Puget Sound SST and Salinity
• Race Rocks
temperature and
salinity is well
correlated with the
Puget Sound-wide
pattern - since it’s
been monitored since
1917, we’ve used this
record to better
understand the longterm variability of
Puget Sound
oceanography
Race Rocks sea surface
temperature since 1921
• Surface
temperatures for
Puget Sound as
a whole closely
track those at
Race Rocks
• Note the large
year-to-year
changes,
decadal cycles,
and on longerterm warming
trend
1998
1941
1983
1958
Moore et al 2008
• Document and describe space time patterns
of seasonal, interannual, and interdecadal
variability in Puget Sound environment
• Evaluate the nature of local, regional, and
large-scale forcings on Puget Sound in order
to understand the potential for predicting
environmental changes important for harmful
algal bloom risks
15
Data
• WA DoE Marine Waters Monitoring Program monthly
temperature and salinity profiles from 16 stations for
1993-2002
• Biannual (summer/winter) UW PRISM transects from 40
stations from 1998-2003
• DFO monthly average Race Rocks SST and SSS from
1937-present
• USGS stream gage data, 1950-present
• PFEL monthly mean upwelling index at 48N, 1950-2002
• US Climate Division Data (temperature), 1950-2002
• Large scale climate indices: NPI, PDO, Nino3.4, 19502002
Sampling
locations
17
Climatological Mean Temperature
Profiles
• Pronounced
seasonal
warming with
surface
intensified
warming most
pronounced in
Whidbey, Hood
Canal, and south
Sound subbasins
18
Climatological Mean Salinity Profiles
•
surface freshening
varies by subbasin:
– south sound
and Hood
Canal in wtr
– Whidbey
Basin in
wtr/spr
– North Sound
in summer
19
EOF analysis of MWM profile data
•
•
leading EOF/PC
captures a substantial
fraction of the total
variance in profiles for
all 16 stations
– Temperature 42%
– Salinity 58%
– Density 56%
PC’s highlight strong
interannual variability in
the 1993-2002 period of
record
eigenvalues
PC1 scores
20
EOF analysis of MWM profile data
•
The loading vectors for
PC1 of temperature,
salinity (at right), and
density all show large
positive values at all
depths for all stations
– The leading PCs
represent depth and
area averaged
variations in
temperature, salinity,
and density at all 16
stations in Puget
Sound
Loading vectors for PC1S
21
We use Race Rocks SST and SSS as
a proxy for PC1T, PC1S, and PC1D to
increase our sample sizes
Correlations with
PCs for 1993-2002
JFM
AMJ
JAS
OND
Race Rocks SST
with PC1T
.868***
.748***
.456
.748***
Race Rocks SSS
with PC1D
.733
.832
.804**
.817***
Race Rocks SSS
with PC1S
.733
.823*
.886***
.827***
Statistical significance at 90%, 95%, and 99% confidence intervals are
indicated by *, **, and ***, respectively.
Correlation analysis
Race Rocks SST and SSS with local
to large scale indices, 1951-2002;
degrees of freedom are noted with
subscripts
• Puget sound streamflow is
significantly correlated with
SSS for winter, spring, and
summer
• SST is most strongly
correlated with regional air
temperature in all seasons,
but correlations with large
scale indices are also
significant in winter
Summary and conclusions
• Analysis of monthly T and S profiles reveals basin-wide
coherence in oceanographic properties at seasonalinterannual time scales
• We use longer time series of SST and SSS from Race
Rocks to evaluate correlations between Puget Sound
properties and local to large scale drivers
– Local air temperature is highly correlated with SST in all
seasons, while freshwater inflow is highly correlated with SSS for
all seasons
– Large scale influences (indicated by ENSO, PDO, and Aleutian
Low indices) most prominent in winter SST, but winter SST
effects persist for the following 2 to 3 seasons, and this indicates
relatively good prospects for predicting Puget Sound
temperature variations one to a few seasons into the future
• There are strong warming trends in Race Rocks SST in
the period since 1970, so recent period of MWM and
PRISM sampling is unique in at least the past ~85 years
Profiles during
extreme periods
• Vertical profiles of
temperature, salinity
and density at station
CMB003 for months
when PC1T, PC1S
and PC1D,
respectively, showed
extreme positive
(top) and negative
(bottom) anomalies.
25
PRISM cruise temperature transects:
1998-2003
26
PRISM cruise salinity transects: 1998-2003
27
PRISM cruise density transects:
6-yr means for 1998-2003
28
Olga air temperature since 1891
Warming trend at Race Rocks, and
throughout Puget Sound, isn’t caused solely
by the PDO
Race Rocks SST anomaly
PDO contribution to Race Rocks SST anomaly
Residual Race Rocks SST anomaly (after removing PDO part)
warming from 1901-2005 was global
Globally averaged, the planet is now about 0.75°C warmer
than it was in 1860, based upon dozens of high-quality long
records using thermometers worldwide, including land and
ocean (IPCC 2007).
Climatological Mean Density Profiles
•
•
•
Seasonal mean
density changes
generally follow
salinity changes
Whidbey Basin and
Hood Canal are
strongly stratified
year-round
North and central
basins tend to be
stratified only in
spring/summer
32
Lag correlations: large scale indices
and Race Rocks SST and SSS
1950-2002
Race Rocks SST
Race Rocks SSS
NPI
NPI
ENSO
ENSO
PDO
PDO
33