NCAR Southern Ocean Workshop Sjoerd Groeskamp · NCAR Southern Ocean Workshop Sjoerd Groeskamp...
Transcript of NCAR Southern Ocean Workshop Sjoerd Groeskamp · NCAR Southern Ocean Workshop Sjoerd Groeskamp...
NCAR Southern Ocean Workshop Sjoerd Groeskamp
10-04-2017
Could Cabbeling play a limiting role for the surface to interior pathway of Anthropogenic Carbon in the Southern Ocean?
Granite Beach, South Coast Track, Tasmania, Australia.
Mixing directions in the ocean
KH∇HC, Horizontal Mesoscale Stirring
KI∇NC, Isopycnal Mesoscale StirringD∇C, Isotropic small-scale Stirring
Water Mass Transformation Nonlinear Equation of State
Salinity
Tem
pera
ture
SmaxSmidSmin
Tmin
Tmid
Tmax
Mesoscale Mixing
Cabbeling
Simple EOS:
Reverse sign of yb
Find arguments based on Observation.Find arguments based on Observation.
Find arguments based on Observation.
Based on Observations: •WOA-2013 (S&T). •Mesoscale Mixing: —> ARGO Based:
Mesoscale mixing
Cole et al. (2015)+extrapolation
Requires Spatial Variation Eddy Diffusivity
FORMATIONAAIW
27-27.5kg/m3
Dense AAIW27.25-27.5
kg/m3
Horizontal 29 Sv 11.9
Isopycnal 4.1 Sv 8.7 Sv
Vertical -29 Sv -2.9
Surface Fluxes -26 Sv -41.2
Ongoing work.
Conclusion: Cabbeling —> important role for AAIW formation
—> Vertical (Tracer) Transport
Zonally Averaged Tendency Sea level Rise
Conclusion:
Cabbeling —> important role for AAIW formation —> Vertical (Tracer) Transport
Question:
Where is the cabbeling coming from?
Saenko and Weaver 2001: Wind Stress Applied to:
Open water and sea ice.
Open water only (=90% ice free)
Sea Ice only
Everywhere, but not to sea ice.
No AAIW formation
Abernathey et al. (2016): Ice Melt in AAIW area.From: SOSE
Their Figure 3b
Freshwater Influx from ice melt.
Warm Salty SAMW influx
Enhanced Mixing byEddies in Southern Ocean.
Cabbeling
Anthropogenic Carbon Circulation The (CA,𝝈0) Volumetric Streamfunctions
Doos and Webb (1995)Nycander et al (2006)Ferrari and Ferreira (2011)Zika et al (2012)Doos et al (2012)Groeskamp et al (2014a,b, 2016b, 2017)
Streamfunction Papers
Anthropogenic Carbon Circulation The (CA,𝝈0) Streamfunctions
Anthropogenic Carbon Circulation The (CA,𝝈0) Streamfunctions
Anthropogenic Carbon Circulation The (CA,𝝈0) Streamfunctions
1) Surface fluxes redistributed by circulation.
2) Circulation and mixing accumulate CA in AAIW range.
3) About 9 Sv of Dense AAIW formation. 4) AAIW formation important part of CA
circulation.
Question:Is cabbeling a limiting factor for CA subduction?
Schematic of resulting Circulation
Conclusions:• Cabbeling significant for AAIW formation (Nycander et al 2015,
Groeskamp et al 2016).
• Anthropogenic Carbon subducted with AAIW
• Anthropogenic Carbon accumulating in the AAIW region.
Questions:• If Sea Ice melt creates S&T contrast that allows for AAIW, what happens
when sea-ice flux changes?
• Is there a seasonality in AAIW formation?
• How does the AAIW formation influence subduction of tracers and specifically Anthropogenic Carbon.
Mixing in the ocean
Conclusions/Future Work (1/3)•Cabbeling significant for AAIW formation.
•Streamfunction for Tracer-Tracer coordinates.
•Applied to S&T to understand water mass transformation and heat and salt transport (and mixing).
•Applied to CA and 𝝈0, to understand CA accumulation and redistribution.
•In this model: •TW: Uptake = Loss.
—> Large CA transport: from TW to SAMW. •CA Accumulation: —> Mostly SAMW/AAIW. •AAIW: Important for surface -> Interior CA transport. •S.O. Eddies: Important for surface -> Interior CA transport. •NADW: Small but DEEP surface -> Interior CA transport. •AABW not so much.
Diapycnal Redistribution:Transport and Accumulation
TW to SAMW Eddies and Seasonal Cycle
NADW
Diapycnal Redistribution:Transport and Accumulation