Uptake and sequestration of atmospheric CO<sub>2</sub> in the Labrador Sea deep convection region

DeGrandpre, M. D.; Körtzinger, Arne; Send, Uwe; Wallace, Douglas W.R.; Bellerby, R. G. J.

doi:10.1029/2006gl026881

Cited by 35 publications

(39 citation statements)

References 22 publications

(36 reference statements)

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“…Sea ice variability in the Labrador Sea and Baffin Bay (LS&BB) is of climatic interest because of its relationship to deep convection and mode water formation (Visbeck et al 1995;Pickart et al 2002), its role in modulating carbon uptake and sequestration (DeGrandpre et al 2006), and its influence on Northern Hemisphere atmospheric circulation patterns (Deser et al 2004). The maximum wintertime extent of seasonal sea ice in the Labrador Sea, monitored via satellite passive microwave radiometry since the late 1970s, has generally declined since the early 1990s (Fig.…”

Section: Introductionmentioning

confidence: 99%

Hydrographic Preconditioning for Seasonal Sea Ice Anomalies in the Labrador Sea

Fenty

Heimbach

2013

Journal of Physical Oceanography

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This study investigates the hydrographic processes involved in setting the maximum wintertime sea ice (SI) extent in the Labrador Sea and Baffin Bay. The analysis is based on an ocean and sea ice state estimate covering the summer-to-summer 1996/97 annual cycle. The estimate is a synthesis of in situ and satellite hydrographic and ice data with a regional coupled 1 /38 ocean-sea ice model. SI advective processes are first demonstrated to be required to reproduce the observed ice extent. With advection, the marginal ice zone (MIZ) location stabilizes where ice melt balances ice mass convergence, a quasi-equilibrium condition achieved via the convergence of warm subtropical-origin subsurface waters into the mixed layer seaward of the MIZ.An analysis of ocean surface buoyancy fluxes reveals a critical role of low-salinity upper ocean (100 m) anomalies for the advancement of SI seaward of the Arctic Water-Irminger Water Thermohaline Front. Anomalous low-salinity waters slow the rate of buoyancy loss-driven mixed layer deepening, shielding an advancing SI pack from the warm subsurface waters, and are conducive to a positive surface meltwater stabilization enhancement (MESEM) feedback driven by SI meltwater release. The low-salinity upper-ocean hydrographic conditions in which the MESEM efficiently operates are termed sea ice-preconditioned waters (SIPW).The SI extent seaward of the Thermohaline Front is shown to closely correspond to the distribution of SIPW. The analysis of two additional state estimates (1992/93, 2003/04) suggests that interannual hydrographic variability provides a first-order explanation for SI maximum extent anomalies in the region.

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Section: Introductionmentioning

confidence: 99%

Hydrographic Preconditioning for Seasonal Sea Ice Anomalies in the Labrador Sea

Fenty

Heimbach

2013

Journal of Physical Oceanography

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“…Deep water formation coupled with strong winds, and high rates of primary production in spring and summer result in this region of the subpolar North Atlantic acting as a strong sink for atmospheric carbon dioxide (DeGrandpre et al, 2006;Pérez et al, 2008). Over the past two decades an increase in surface water pCO 2 at a rate greater than that of the atmosphere has been observed in the Irminger Sea Bates et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Can Empirical Algorithms Successfully Estimate Aragonite Saturation State in the Subpolar North Atlantic?

et al. 2017

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The aragonite saturation state ( Ar ) in the subpolar North Atlantic was derived using new regional empirical algorithms. These multiple regression algorithms were developed using the bin-averaged GLODAPv2 data of commonly observed oceanographic variables [temperature (T), salinity (S), pressure (P), oxygen (O 2 ), nitrate (NO − 3 ), phosphate (PO 3− 4 ), silicate (Si(OH) 4 ), and pH]. Five of these variables are also frequently observed using autonomous platforms, which means they are widely available. The algorithms were validated against independent shipboard data from the OVIDE2012 cruise. It was also applied to time series observations of T, S, P, and O 2 from the K1 mooring (56.5 • N, 52.6 • W) to reconstruct for the first time the seasonal variability of Ar . Our study suggests: (i) linear regression algorithms based on bin-averaged carbonate system data can successfully estimate Ar in our study domain over the 0-3,500 m depth range (R 2 = 0.985, RMSE = 0.044); (ii) that Ar also can be adequately estimated from solely non-carbonate observations (R 2 = 0.969, RMSE = 0.063) and autonomous sensor variables (R 2 = 0.978, RMSE = 0.053). Validation with independent OVIDE2012 data further suggests that; (iii) both algorithms, non-carbonate (MEF = 0.929) and autonomous sensors (MEF = 0.995) have excellent predictive skill over the 0-3,500 depth range; (iv) that in deep waters (>500 m) observations of T, S, and O 2 may be sufficient predictors of Ar (MEF = 0.913); and (iv) the importance of adding pH sensors on autonomous platforms in the euphotic and remineralization zone (<500 m). Reconstructed Ar at Irminger Sea site, and the K1 mooring in Labrador Sea show high seasonal variability at the surface due to biological drawdown of inorganic carbon during the summer, and fairly uniform Ar values in the water column during winter convection. Application to time series sites shows the potential for regionally tuned algorithms, but they need to be further compared against Ar calculated by conventional means to fully assess their validity and performance.

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“…The uncertainty of the atmospheric history is < 1 % for SF 6 and CFC-12, whereas for low concentrations of CFC-12 an error of ≤ 4 % should be assumed due to the time period prior reliable CFC measurements (Tanhua et al, 2008;Walker et al, 2000). The input functions depend on the degree of saturation during a water-mass formation which is influenced by wind speed, mixed layer depth, convection velocity, pressure and temperature drops as well as the atmospheric emission increase of a tracer, resulting in an approximate 10 % propagation of uncertainty (Haine and Richards, 1995;DeGrandpre et al, 2006;Tanhua et al, 2008). Furthermore, there are some regions were SF 6 has been used for release experiments (e.g., 1996 in the Greenland Sea gyre; Watson et al, 1999), which could produce an offset in concentrations.…”

Section: Uncertaintiesmentioning

confidence: 99%

Ventilation of the Mediterranean Sea constrained by multiple transient tracer measurements

Stöven

Tanhua

2014

Ocean Sci.

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Abstract. Ventilation is the primary pathway for atmosphere-ocean boundary perturbations, such as temperature anomalies, to be relayed to the ocean interior. It is also a conduit for gas exchange between the interface of atmosphere and ocean. Thus it is a mechanism whereby, for instance, the ocean interior is oxygenated and enriched in anthropogenic carbon. The ventilation of the Mediterranean Sea is fast in comparison to the world ocean and has large temporal variability. Here we present transient tracer data from a field campaign in April 2011 that sampled a unique suite of transient tracers (SF 6 , 3 H and 3 He) in all major basins of the Mediterranean. We apply the transit time distribution (TTD) model to the data in order to constrain the mean age, the ratio of the advective / diffusive transport and the number of water masses significant for ventilation.We found that the eastern part of the eastern Mediterranean can be reasonably described with a one-dimensional inverse Gaussian TTD (IG-TTD), and thus constrained with two independent tracers. The ventilation of the Ionian Sea and the western Mediterranean can only be constrained by a linear combination of IG-TTDs. We approximate the ventilation with a one-dimensional, two inverse Gaussian TTD (2IG-TTD) for these areas and demonstrate a possibility of constraining a 2IG-TTD from the available transient tracer data. The deep water in the Ionian Sea has a mean age between 120 and 160 years and is therefore substantially older than the mean age of the Levantine Basin deep water (60-80 years). These results are in contrast to those expected by the higher transient tracer concentrations in the Ionian Sea deep water. This is partly due to deep water of Adriatic origin having more diffusive properties in transport and formation (i.e., a high ratio of diffusion over advection), compared to the deep water of Aegean Sea origin that still dominates the deep Levantine Basin deep water after the Eastern Mediterranean Transient (EMT) in the early 1990s. The tracer minimum zone (TMZ) in the intermediate of the Levantine Basin is the oldest water mass with a mean age up to 290 years. We also show that the deep western Mediterranean has contributed approximately 40 % of recently ventilated deep water from the Western Mediterranean Transition (WMT) event of the mid-2000s. The deep water has higher transient tracer concentrations than the mid-depth water, but the mean age is similar with values between 180 and 220 years.

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Uptake and sequestration of atmospheric CO₂ in the Labrador Sea deep convection region

Cited by 35 publications

References 22 publications

Hydrographic Preconditioning for Seasonal Sea Ice Anomalies in the Labrador Sea

Hydrographic Preconditioning for Seasonal Sea Ice Anomalies in the Labrador Sea

Can Empirical Algorithms Successfully Estimate Aragonite Saturation State in the Subpolar North Atlantic?

Ventilation of the Mediterranean Sea constrained by multiple transient tracer measurements

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Uptake and sequestration of atmospheric CO2 in the Labrador Sea deep convection region

Cited by 35 publications

References 22 publications

Hydrographic Preconditioning for Seasonal Sea Ice Anomalies in the Labrador Sea

Hydrographic Preconditioning for Seasonal Sea Ice Anomalies in the Labrador Sea

Can Empirical Algorithms Successfully Estimate Aragonite Saturation State in the Subpolar North Atlantic?

Ventilation of the Mediterranean Sea constrained by multiple transient tracer measurements

Contact Info

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Uptake and sequestration of atmospheric CO₂ in the Labrador Sea deep convection region