Winter Lead Convection
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Transcript of Winter Lead Convection
Winter Lead Convection
The Study of Environmental Arctic Change (SEARCH) and the Barrow
Cabled Observatory
Presentation at Science and Education Opportunities for an Arctic Cabled Seafloor Observatory
February 7-8, 2005
Jamie Morison
Polar Science Center, University of Washington
SEARCH Motivation
The Arctic has been characterized in recent decades by a complex of
significant, interrelated, pan-Arctic changes (Unaami).
Examples
• Decreased sea level atmospheric pressure,
• Increased air temperature over most of the Arctic,
• More cyclonic ocean circulation and rising coastal sea level,
• Warmer Atlantic waters,
• Reduced sea ice cover,
• Warming of permafrost
• The physical changes of Unaami impact ecosystems and society.
Complex of change appears related to a spin up of the Northern Hemisphere atmospheric Polar Vortex.
Complex of Arctic change is a possible component of climate change.
Motivates a program of long-term observations, analysis, and modeling
Implementation Strategy at SEARCH Web site:Implementation Strategy at SEARCH Web site:http://psc.apl.washington.edu/search/index.html
Current Activities atCurrent Activities athttp://psc.apl.washington.edu/search/Activities/activities.html
Eight SEARCH Activities Areas include:Eight SEARCH Activities Areas include:- DTO: Distributed Terrestrial Observatories
- DMO: Distributed Marine Observatories
- LAO: Large-scale Atmospheric Observatories
- DQU: Detecting and Quantifying Unaami and Other Modes of
Variability- LGC: Linkages and Global Coupling
- ASR: Arctic System Reanalysis
- SEI: Social and Economic Interaction
- SOR: Social Response
SEARCH ImplementationSEARCH Implementation
Distributed Terrestrial ObservatoriesDistributed Terrestrial Observatories
Russia
Nor
AlaskaEureka
Alert
Greenland
Canada
Thule
Tiksi
Arcic Ocean
Distributed TerrestrialObservatories
Kolyma R
Lena R
Ob R
Mackenzie R
Yukon R
Yenisey R
x
x
x
x
x
x
x
x
x x
x
x
x
xx
x Extensive Site
Intermediate Site(e.g., ITEX, CEON)
Intensive Site
Barrow
Cherksiy
Svalbard
Resolute
Abisko
BonanzaToolik
Large-scale Atmospheric ObservatoriesLarge-scale Atmospheric Observatories
Norway
Greenland
Canada
Thule
Resolute
AbiskoKolyma R
Lena R
Ob R
Mackenzie R
Yukon R
Yenisey R
Cherksiy
Large-scale AtmosphericObservatoriesAlaska
Russia
Eureka
IABP Drifting Buoys
Automated Drifting Stations
DTO Intensive Site
DTO Intermediate Site
x DTO Extensive Site
x
x
x
x
x
x
x
x
x x
x
x
x
xxBonanza
Toolik
GCOS - GTOSGCOS - GTOS
Remote Sensing, e.g. TOVSRemote Sensing, e.g. TOVS
AlertAlertBarrowBarrow
SvalbardSvalbard
Major Weather StationsMajor Weather Stations
TiksiTiksi
DTO Sites
DMO: Distributed Marine Observatories
Make large-scale atmospheric, oceanographic, sea ice and ecosystem observations in the marine environment.
SEARCH Implementation Strategy available at SEARCH Implementation Strategy available at http://psc.apl.washington.edu/search/index.htmlhttp://psc.apl.washington.edu/search/index.html
Distributed Marine ObservatoriesDistributed Marine Observatories
Norway
Eureka
Alert
Greenland
Canada
Thule
Barrow
Svalbard
Resolute
AbiskoKolyma R
Lena R
Ob R
Mackenzie R
Yukon R
Yenisey R
Russia
Tiksi
Cherksiy
Distributed MarineObservatories
IABP Drifting Buoys
2
34
5
10
6
7
8
11
12
1
Ocean Pathway Moorings
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13
15
14
16
Cross Shelf Exchange Moorings
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20
19
18
Basin Moorings
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Gateway Moorings
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Shelf Moorings & Surveys
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Clic Hydrographic SectionsOther Sections
ASOF Hydrographic Sections
38
39
40
Automated Drifting StationsUpward Looking Sonars
DMO Philosophy
Scales are pan-Arctic and decadal. Therefore the DMO emphasis is on:
And because startup is urgent: - Use of proven, existing technologies
- Basin-wide coverage
- Long, relatively low res time-series
So, what role can a high-tech, high-bandwidth cabled observatory at
Barrow have in DMO?
Two DMO elements near Barrow:
• Ocean pathway moorings
• Cross shelf exchange moorings
Role for high-bandwidth, localized measurements particularly in
• Cross shelf exchange mooring function of DMO, and
• The Linkages and Global Coupling (LGC) activity area
Processes in the shelf and slope region are important to ventilation of the deep ocean, e.g.
These processes tend to be intermittent and spatially variable.
• Generation of eddies that move into the basin
• Cross shelf exchange driven by buoyancy flux in the Seasonal Ice Zone (SIZ) and winter shore leads and polynyas
AIDJEX Lead Experiment, 1974
Indication of cross-shelf exchange
Example of bottom boundary layer generated by Barrow shore lead (ALEX, 1974)
Consider buoyancy flux and cross shelf exchange.
WIND MOVES PACK ICE AWAY FROMSHOREFAST ICE
HALINE CONVECTIONSHELF BREAK FRONT
SHORE LEAD
SHOREFAST ICE
+
Consider buoyancy flux and cross shelf exchange.
These processes create density structure parallel to shore and cross shore pressure gradients, which drive alongshore currents.
WIND
WIND SWEEPS NEW ICE OFFSHORE
HALINE CONVECTIONSHELF BREAK
FRONT
COASTAL POLYNYA
+
So where does cross-shelf exchange occur?
In the surface and bottom boundary layers where flow moves down pressure gradient.
WIND
WIND SWEEPS NEW ICE OFFSHORE
HALINE CONVECTIONSHELF BREAK
FRONT
COASTAL POLYNYA
+
How would we use the BCO to measure shelf processes?
Shore Lead
Convective Plume
SalinityProfile
BottomBoundaryLayer
Monitoring Winter Shelf Convection With the BCO
Pack Ice Fast Ice
Fixed CTD, ABPR, ADCP, ULS Cable
Turbulent InstrumentCluster "Pods"
ROV Hangar
Instrumented ROVServicing Arrays
AUV HangarAUV NavXponders
AUV NavXponders
AUV
Iridium, Met SensorsHoming Beacon
Supercoolometer:Seamore ROV
SBE 39 T Probe
Heater
SBE-19+Temperature & Conductivity
Optical Backscatter
Water In
JAMSTEC UROV 7k Remotely Operated
Vehicle
Battery OperatedFiber Optic Link
KAIKO Hanger
UROV
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
TIC
SonTekADVOcean (5 MHz)
SBE 03 thermometer
SBE 07 micro-conductivity meter
SBE 04 conductivitymeter
SonTek Instrument Cluster
.
8
IceT-string
ROV-CTD
0.6 m
1 m
Van Mijen Fjord Instruments
Miles McPhee Turbulent Inst Cluster
Autonomous Flux Buoy
Tim Stanton Flux Buoy
The Autonomous Microconductivity-Temperature Vehicle (AMTV)
1.6 m
Weight = 36.2 kgSpeed = 1.0-1.6 m/s
Micro T and C Sensors
Altimeter
Autonomous Micro-conductivity Temperature Vehicle (AMTV)
RecoveryBarb
HomingHydrophones
Tracking Hydrophone
Figure 1. The AMTV during testing at the SHEBA Ice Station, August, 1998.
QuickTime™ and aDV/DVCPRO - NTSC decompressor
are needed to see this picture.
AMTV
AMTV Results SHEBA Summer Lead Study, Day 219.9
Under Lead
S constant?
Cooler
Back Toward Ice
Warmer
FresherS constant &S’ small
Cooler &T’ small
Under Ice
From Hayes Dissertation, 2003
AMTV Turbulence on 219.9
S’ and T’ Vigorous Under Lead
Turbulence Significant Under Lead
S’ and T’ Reduced Under Ice
Turbulence EnhancedUnder Ice? Lower Frequency
From Hayes Dissertation, 2003
AMTV Turbulent Fluxes on 219.9, 1998 at SHEBA Summer Lead
Turbulent Stress, u*=()1/2, Increased Under Ice
From Hayes Dissertation, 2003
98 W m-2 144 W m-2
Substantial Turbulent Heat and Salt Flux in the Lead, Reduced Fluxes Under Ice
2.4x10-5 kg m-2 s-11.7x10-5 kg m-2 s-1 1.9x10-5
Conclusions:
The BCSO can play an important part in SEARCH.
Focus as an intensive observing point for shelf-basin processes critical for the large scale behaviour of the marine environment
The End