Physical variability associated to the formation of water stratification events and emergence of anoxia in Paracas Bay (14° S) downstream
the main Peruvian coastal upwelling cell
Lander Merma, Dimitri Gutiérrez, François Colas, Edgart Flores, Arturo Aguirre, David Correa, Sonia Sánchez and Alberto Lorenzo
Mail: [email protected]
INTRODUCTION
• Most intense alongshore winds
• Main Peruvian coastal upwelling cell
• Upwelling persists throughout the year
• Paracas Bay is downstream the upwelling cell and surrounded by Paracas Peninsula
78ºW 77ºW 76ºW15°S
14°S
13°S
Pisco
78ºW 77ºW 76ºW15°S
14°S
13°S
Pisco
Gutiérrez et al. 2011
1516171819202122232425SST (°C)
Jan-Feb-Mar
Jul-Aug-Sep
13.85°S
13.8°S
13.75°S
13.7°S
13.65°S
76.3°W 76.25°W 76.2°W
PiscoRiver
ParacasBay
San MartinHarbour
Aquaculturezone
Tourism andurban area
Fishingindustryzone
San AndresHarbour
Airport
Pisco City
ParacasNational Reserve
INTRODUCTION
• Paracas Bay: a transition zone between Coastal Upwelling System and inshore marine environment.
• Paracas Bay: a small dimensions embayment but very important in Peru: Fishery and trade harbours Platform: terminal (Natural
gas by-products exportation)
One of the most important aquaculture zones
One of the most important tourism destination
Critical environmental phenomena (HABs, water stratified conditions, anoxia, mass mortality) still poorly understood.
78ºW 77ºW 76ºW15°S
14°S
13°S
Pisco
78ºW 77ºW 76ºW15°S
14°S
13°S
Pisco
Gutiérrez et al. 2011
1516171819202122232425SST (°C)
Jan-Feb-Mar
Jul-Aug-Sep
-13°40'
-13°43'
-13°46'
-76°17'-76°19' -76°15'
El Chaco
La Puntilla
Playa Lobería
Río Pisco
San Andrés
-76°13'
-13°49'
O2mL/L
0 0.25 0.5 0.75 1
INTRODUCTION
OBJECTIVE:
Describe physical factors that lead to the formation of strong stratification events and to explain the influence of these on the emergence of anoxia in Paracas Bay.
78ºW 77ºW 76ºW15°S
14°S
13°S
Pisco
78ºW 77ºW 76ºW15°S
14°S
13°S
Pisco
Gutiérrez et al. 2011
1516171819202122232425SST (°C)
Jan-Feb-Mar
Jul-Aug-Sep
13.85°S
13.8°S
13.75°S
13.7°S
13.65°S
76.3°W 76.25°W 76.2°W
PiscoRiver
ParacasBay
San MartinHarbour
Aquaculturezone
Tourism andurban area
Fishingindustryzone
San AndresHarbour
Airport
Pisco City
ParacasNational Reserve
76.7°W 76.5°W 76.3°W 76.1°W
14.2°S
14°S
13.8°S
13.6°S
Satellitedata
AirportP1
P2
METHODS High frequency (daily) data from 2006-2015: • Wind favorable to upwelling
(QUICKSCAT & ASCAT) • Local wind (Pisco Airport) • Surface and bottom water
temperature (△T): P1 • River discharges flow (ANA)
High frequency (hourly) data from 2015 (March to December) registered by data loggers: P2 • Surface and bottom water
temperature (△T) and bottom dissolved oxygen (optode sensor):
Non-periodic data ( , IMARPE in situ surveys) • Surface and bottom water
temperature (△T) • Surface salinity • Bottom dissolved oxygen
Time series: Analysis at monthly (averages) and daily scale: Cross correlation, wavelets analysis. Non-periodic data : Simple correlation.
RESULTS:
Average conditions (monthly scale)
△Te
mper
ature
(°C
)
Loca
l W
ind (
ms-
1)
Upw
ell. W
ind (
ms-
1)
Riv
er flo
w (
m3s-
1)
RESULTS:
Average conditions (monthly scale)
△Te
mper
ature
(°C
)
Loca
l W
ind (
ms-
1)
Upw
ell. W
ind (
ms-
1)
Riv
er flo
w (
m3s-
1)
RESULTS:
Average conditions (monthly scale)
△Te
mper
ature
(°C
)
Loca
l W
ind (
ms-
1)
Upw
ell. W
ind (
ms-
1)
Riv
er flo
w (
m3s-
1)
RESULTS:
Cross-correlation of ΔTemperature VS physical factors (monthly scale)
-10 -5 0 5 10
-1.0
-0.5
0.0
0.5
1.0
Lag
Cro
ss c
orre
latio
n
Upwelling index VS Temperature
-10 -5 0 5 10
-1.0
-0.5
0.0
0.5
1.0
Lag
Cro
ss c
orre
latio
n
Local wind VS Temperature
-10 -5 0 5 10
-1.0
-0.5
0.0
0.5
1.0
Lag
Cro
ss c
orre
latio
n
River flow VS TemperatureUpwelling wind
ΔTemperature
River discharges flow
High frequency (daily scale) Wavelet analysis of daily anomalies
RESULTS:
Wind favourable to upwelling
Local wind Wavelet analysis of daily anomalies
RESULTS:
-20 -10 0 10 20
-1.0
-0.5
0.0
0.5
1.0
Lag
Cro
ss c
orre
latio
n
Local wind VS Upwelling index
RESULTS: Cross-correlation of upwelling and local winds anomalies
Upwelling wind
-20 -10 0 10 20
-1.0
-0.5
0.0
0.5
1.0
Lag
Cro
ss c
orre
latio
n
Temperature VS River flow
-20 -10 0 10 20
-1.0
-0.5
0.0
0.5
1.0
Lag
Cro
ss c
orre
latio
n
Temperature VS Upwelling index
-20 -10 0 10 20
-1.0
-0.5
0.0
0.5
1.0
Lag
Cro
ss c
orre
latio
n
Temperature VS Local Wind
RESULTS: Cross-correlation between Δtemperature anomalies and physical factors anomalies
wind
Correlation between anomalies of stratification (ΔTemperature) and physical factors considering summer months data only
Even in summer months only there is no correlation between river discharges flow and ΔTemperature
anomalies
anomalies
anomalies
anomalies
R= -0.50, p<0.01
R= -0.52, p<0.01
R= -0.49, p<0.01
Upwell wind
-13°40'
-13°43'
-13°46'
-76°17'-76°19' -76°15'
El Chaco
La Puntilla
LoberiaBeach
PiscoRiver
SanAndresHarbour
-76°13'
-13°49'
(°C)
16
17
18
19
20
21
22
23
24
25
26-13°40'
-13°43'
-13°46'
-76°17'-76°19' -76°15'
El Chaco
La Puntilla
LoberiaBeach
PiscoRiver
SanAndresHarbour
-76°13'
-13°49'
(°C)
16
17
18
19
20
21
22
23
24
25
26 -13°40'
-13°43'
-13°46'
-76°17'-76°19' -76°15'
El Chaco
La Puntilla
LoberiaBeach
PiscoRiver
SanAndresHarbour
-76°13'
-13°49'
(°C)
16
17
18
19
20
21
22
23
24
25
26
-13°40'
-13°43'
-13°46'
-76°17'-76°19' -76°15'
El Chaco
La Puntilla
LoberiaBeach
PiscoRiver
SanAndresHarbour
-76°13'
-13°49'
ups
31
31.5
32
32.5
33
33.5
34
34.5
35
35.5-13°40'
-13°43'
-13°46'
-76°17'-76°19' -76°15'
El Chaco
La Puntilla
LoberiaBeach
PiscoRiver
SanAndresHarbour
-76°13'
-13°49'
ups
31
31.5
32
32.5
33
33.5
34
34.5
35
35.5-13°40'
-13°43'
-13°46'
-76°17'-76°19' -76°15'
El Chaco
La Puntilla
LoberiaBeach
PiscoRiver
SanAndresHarbour
-76°13'
-13°49'
ups
31
31.5
32
32.5
33
33.5
34
34.5
35
35.5
8 apr 2015 3 mar 2015 19 mar 2015
Surface salinity
Surface temperature
Non periodic data (case: March-April 2015)
Correlation between non periodic data (summer months only) and physical factors anomalies
Non periodic data
RESULTS:
R= -0.40, p<0.01
R= -0.52, p<0.01
R= 0.51, p<0.01
R= 0.47, p<0.05
R= 0.75, p<0.01
anomalies
anomalies
anomalies
Upwell wind
Some hypoxia and anoxia events also occur at normal values of salinity and Δtemperature: another mechanisms (milky cold waters)
RESULTS: Non periodic data Correlation between non periodic data (all seasons)
ΔTemperature exhibits the highest levels at lowest levels of surface salinity, and at the same time dissolved bottom oxygen is in hypoxic levels (<2mL/L) or there is anoxia.
Bottom
RESULTS: High frequency data inside Paracas Bay (P2) based on surface and bottom temperature sensors and bottom optode oxygen sensor
01
23
45
67
20
15
-03
-30
20
15
-04
-06
20
15
-04
-13
20
15
-04
-20
20
15
-04
-27
20
15
-05
-04
20
15
-05
-11
20
15
-05
-18
20
15
-05
-25
20
15
-06
-01
20
15
-06
-08
20
15
-06
-15
20
15
-06
-22
20
15
-06
-29
20
15
-07
-06
20
15
-07
-13
20
15
-07
-20
20
15
-07
-27
20
15
-08
-03
20
15
-08
-10
20
15
-08
-17
20
15
-08
-24
20
15
-08
-31
20
15
-09
-07
20
15
-09
-14
20
15
-09
-21
20
15
-09
-28
20
15
-10
-05
20
15
-10
-12
20
15
-10
-19
20
15
-10
-26
20
15
-11
-02
20
15
-11
-09
20
15
-11
-16
20
15
-11
-23
20
15
-11
-30
20
15
-12
-07
20
15
-12
-14
20
15
-12
-21
20
15
-12
-28
20
16
-01
-04
△Temp Oxígeno fondo
CONCLUSIONS:
• Weaker coastal wind intensity and strong river discharges condition the development of water stratification in Paracas Bay particularly in summer.
• The formation of strong stratification events is due to increases in the
surface temperature as a result of upwelling wind and local wind calms that allow the arriving of low surface salinity waters to the bay.
• Bottom oxygen is near or in hypoxic levels most of the time in Paracas Bay due to the low oxygen content of the incoming upwelling waters, but strong summer stratification events contribute to the emergence and spread of anoxia.
