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Sabine Mecking

Principal Oceanographer

Affiliate Assistant Professor, Oceanography

Email

smecking@apl.washington.edu

Phone

206-221-6570

Research Interests

Large-Scale Ocean Circulation, Climate Variability, Tracers, Biogeochemical Cycling

Biosketch

Dr. Mecking's research interests are in interdisciplinary oceanography involving large-scale ocean circulation, ocean mixing, tracer ages, biogeochemical cycling, and thermocline ventilation. One particular focus is how these processes are affected by decadal-scale climate variability and how they relate to the uptake and storage of carbon in the ocean. Her work involves participation in hydrographic cruises, data analysis, and combining data with general circulation models through collaboration with modelers. Dr. Mecking joined APL-UW in 2006.

Education

Vordiplom Oceanography, Universitat Hamburg, Germany, 1993

M.S. Oceanography, University of Washington, 1997

Ph.D. Oceanography, University of Washington, 2001

Projects

Modeling CFC and SF6 Mixed Layer Boundary Conditions

Chlorofluorocarbons (CFCs) and sulfur hexafluoride (SF6) are tracers that enter the ocean surface mixed layer through air–sea gas exchange and are then transported into the ocean interior. Because of their long time-scale evolution, these tracers are used to estimate ocean interior ventilation time scales (ages) as well as anthropogenic carbon uptake by the ocean.

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28 Sep 2012

Chlorofluorocarbons (CFCs) and sulfur hexafluoride (SF6) are man-made, transient tracers that enter the ocean surface mixed layer through air–sea gas exchange and that then are transported into the ocean interior as part of the general ocean circulation. Because of their conservative and time-evolving nature, these tracers are widely used to estimate ocean interior ventilation time scales (ages) as well as anthropogenic carbon uptake by the ocean.

Through a variety of model test cases, we quantify the roles of air–sea gas exchange, mixed layer warming/cooling, and entrainment in disrupting the air–sea equilibrium of the tracer concentrations. The model results aid the interpretation of data from global surveys (e.g., WOCE and CLIVAR/CO2 Repeat Hydrography) and observational programs.

Atlantic Ocean: Transport and Divergence of Carbon, Oxygen, and Nutrients

Estimates of the transport and divergence of carbon, oxygen, and nutrients in the Atlantic Ocean are based on two approaches: a multi-box inverse model based on WOCE/JGOFS data, and tracer data sets from the same period.

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29 Nov 2011

This project seeks to provide data-based estimates of the transport and divergence of carbon, oxygen, and nutrients in the Atlantic Ocean based on two approaches: 1) using a multi-box inverse model based on the long line data collected during the WOCE/JGOFS period, and 2) using tracer age data sets from the same time period. This first part is done in collaboration with Alison Macdonald at WHOI. The latter part includes a GCM-based analysis of possible tracer age biases due to mixing, which is performed in collaboration with LuAnne Thompson at UW. The goal of the project is to evaluate the location and magnitude of oceanic uptake/outgassing of CO2 as well as the size of the biological carbon pump (see poster at 2010 Ocean Sciences Meeting). Collaborators: Alison Macdonald (WHOI), LuAnne Thompson (UW). Funding: NSF

Mixed Layer Boundary Conditions of Chlorofluorocarbons in the North Pacific

A series of model experiments with the Hallberg Isopycnal Model (HIM) are used to investigate the mixed layer boundary conditions of CFCs in the North Pacific Ocean and the the implications of possible winter-time undersaturations on the interpretation of CFC-derived age distributions and anthropogenic carbon estimates in the ocean interior.

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28 Nov 2011

The purpose of this research is to perform a series of model experiments with the Hallberg Isopycnal Model (HIM) to investigate 1) mixed layer boundary conditions of CFCs in the North Pacific Ocean and 2) the implications of possible winter-time undersaturations on the interpretation of CFC-derived age distributions and anthropogenic carbon estimates in the ocean interior. The results from the modeling study will be used to aid the interpretation of the U.S. CLIVAR/CO2 Repeat Hydrography data in the North Pacific which consist of the meridional P16N line and zonal P2 line conducted along 152W in 2006 and along 30N in 2004, respectively. The project is performed in collaboration with LuAnne Thompson and Mark Warner at UW. Funding: NOAA

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Publications

2000-present and while at APL-UW

Two decades of Pacific anthropogenic carbon storage and ocean acidification along Global Ocean Ship-based Hydrographic Investigations Program sections P16 and P02

Carter, B.R., and 11 others, including S. Mecking, "Two decades of Pacific anthropogenic carbon storage and ocean acidification along Global Ocean Ship-based Hydrographic Investigations Program sections P16 and P02," Glob. Biogeochem. Cycles, 31, 306-327,doi:10.1002/2016GB005485, 2017.

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1 Feb 2017

A modified version of the extended multiple linear regression (eMLR) method is used to estimate anthropogenic carbon concentration (Canth) changes along the Pacific P02 and P16 hydrographic sections over the past two decades. P02 is a zonal section crossing the North Pacific at 30°N, and P16 is a meridional section crossing the North and South Pacific at ~150°W. The eMLR modifications allow the uncertainties associated with choices of regression parameters to be both resolved and reduced. Canth is found to have increased throughout the water column from the surface to ~1000 m depth along both lines in both decades. Mean column Canth inventory increased consistently during the earlier (1990s–2000s) and recent (2000s–2010s) decades along P02, at rates of 0.53 ± 0.11 and 0.46 ± 0.11 mol C m-2 a-1, respectively. By contrast, Canth storage accelerated from 0.29 ± 0.10 to 0.45 ± 0.11 mol C m-2 a-1 along P16. Shifts in water mass distributions are ruled out as a potential cause of this increase, which is instead attributed to recent increases in the ventilation of the South Pacific Subtropical Cell. Decadal changes along P16 are extrapolated across the gyre to estimate a Pacific Basin average storage between 60°S and 60°N of 6.1 ± 1.5 PgC decade-1 in the earlier decade and 8.8 ± 2.2 PgC decade-1 in the recent decade. This storage estimate is large despite the shallow Pacific Canth penetration due to the large volume of the Pacific Ocean. By 2014, Canth storage had changed Pacific surface seawater pH by –0.08 to –0.14 and aragonite saturation state by –0.57 to –0.82.

Evaluating the use of 1-D transit time distributions to infer the mean state and variability of oceanic ventilation

Zhao, A.E., S. Mecking, L. Thompson, and R.E. Sonnerup, "Evaluating the use of 1-D transit time distributions to infer the mean state and variability of oceanic ventilation," J. Geophys. Res., 121, 6650-6670, doi:10.1002/2016JC011900, 2016.

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10 Sep 2016

An offline tracer transport model transport is used to simulate chlorofluorocarbon (CFCs), sulfur hexafluoride (SF6), oxygen, ideal age, and model transit time distributions (TTDs) to evaluate how well tracers can be used to constrain both the mean state and variability of oceanic ventilation. Using climatological transports, the two-parameter 1-D inverse Gaussian approximation of the model TTD is found to be an adequate representation of ventilation pathways within the parts of the subtropical gyres with simple ventilation dynamics, but a poor approximation for regions with large gradients in ideal age (i.e., near the base of the thermocline and the continental boundaries). TTDs inferred from CFC-12 and SF6 using a Peclet number-based lookup table approach yield poor representations of the model TTD with a consistent bias toward ventilation being strongly dominated by along-isopycnal diffusion. In a run with variable circulation, ideal age is used to track changes in thermocline ventilation. Variability in both apparent oxygen utilization (AOU) and tracer-inferred TTD mean ages inferred using CFC-12 (assuming fixed Peclet number) and dual tracers (SF6 and CFC-12) are well-correlated to ideal age variability in most of the thermocline. Changes in AOU are correlated with ideal age variability in even more regions compared to the TTD ages both horizontally and vertically down to intermediate depths. Generally, when changes in TTD mean age and AOU agreed in sign, correlations of both with ideal age changes were positive indicating the usefulness of tracers in diagnosing ventilation changes.

Evaluating the use of 1-D transit time distributions to infer the mean state and variability of oceanic ventilation

Shao, A.E., S. Mecking, L. Thompson, and R.E. Sonnerup, "Evaluating the use of 1-D transit time distributions to infer the mean state and variability of oceanic ventilation," J. Geophys. Res., 121, 6650-6670, doi:10.1002/2016JC011900, 2016.

More Info

1 Sep 2016

An offline tracer transport model transport is used to simulate chlorofluorocarbon (CFCs), sulfur hexafluoride (SF6), oxygen, ideal age, and model transit time distributions (TTDs) to evaluate how well tracers can be used to constrain both the mean state and variability of oceanic ventilation. Using climatological transports, the two-parameter 1-D inverse Gaussian approximation of the model TTD is found to be an adequate representation of ventilation pathways within the parts of the subtropical gyres with simple ventilation dynamics, but a poor approximation for regions with large gradients in ideal age (i.e., near the base of the thermocline and the continental boundaries). TTDs inferred from CFC-12 and SF6 using a Peclet number-based lookup table approach yield poor representations of the model TTD with a consistent bias toward ventilation being strongly dominated by along-isopycnal diffusion. In a run with variable circulation, ideal age is used to track changes in thermocline ventilation. Variability in both apparent oxygen utilization (AOU) and tracer-inferred TTD mean ages inferred using CFC-12 (assuming fixed Peclet number) and dual tracers (SF6 and CFC-12) are well-correlated to ideal age variability in most of the thermocline. Changes in AOU are correlated with ideal age variability in even more regions compared to the TTD ages both horizontally and vertically down to intermediate depths. Generally, when changes in TTD mean age and AOU agreed in sign, correlations of both with ideal age changes were positive indicating the usefulness of tracers in diagnosing ventilation changes.

More Publications

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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