The Arctic Ocean warms from below

Carmack, Eddy C.; Williams, William J.; Zimmermann, Sarah; McLaughlin, Fiona A.

doi:10.1029/2012gl050890

Cited by 30 publications

(33 citation statements)

References 33 publications

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“…Hydrological features such as the θ-S convexity and O 2 minimum observed within the DTL at the MB stations also support exchanges of CB deep waters toward the MB (Figures 4, 5h, and 9d). Although the direction of exchanges we suggest here conflicts with former hydrological study conclusions that invoked a dominant flux of DTL water above the Mendeleev/Alpha Ridge from the MB toward the CB (e.g., Carmack et al, 2012;Rudels, 2009), Swift et al (1997) (Figures 9b and 12c), we agree with Middag et al (2009) and Roeske et al (2012) that MB bottom water is also made of some colder and fresher Amundsen Basin Deep Water (ABDW) that likely came over the Lomonosov Ridge (between 2,000 and 2,500 m) and sank due to its higher density than the local bottom waters (Timmermans et al, 2005).…”

Section: Lateral Exchanges In Other Areas Of the Amerasian Basin 54contrasting

confidence: 99%

Changes in Circulation and Particle Scavenging in the Amerasian Basin of the Arctic Ocean over the Last Three Decades Inferred from the Water Column Distribution of Geochemical Tracers

et al. 2019

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Since the 1980-1990s, international research efforts have augmented our knowledge of the physical and chemical properties of the Arctic Ocean water masses, and recent studies have documented changes. Understanding the processes responsible for these changes is necessary to be able to forecast the local and global consequences of these property evolutions on climate. The present work investigates the distributions of geochemical tracers of particle fluxes and circulation in the Amerasian Basin and their temporal evolution over the last three decades (from stations visited between 1983 and 2015). Profiles of 230-thorium ( 230 Th) and 231-protactinium ( 231 Pa) concentrations and neodymium isotopes (expressed as ε Nd ) measured in the Amerasian Basin prior to 2000 are compared to a new, post-2000s data set. The comparison shows a large scale decrease in dissolved 230 Th and 231 Pa concentrations, suggesting intensification of scavenging by particle flux, especially in coastal areas. Higher productivity and sediment resuspension from the shelves appear responsible for the concentration decrease along the margins. In the basin interior, increased lateral exchanges with the boundary circulation also contribute to the decrease in concentration. This study illustrates how dissolved 230 Th and 231 Pa, with ε Nd support, can provide unique insights not only into changes in particle flux but also into the evolution of ocean circulation and mixing. Plain Language SummaryThe Arctic Ocean is one of the oceanic regions most affected by climate change. The increasing summer retreat of sea ice allows greater atmosphere-ocean exchanges and light penetration, while land-ocean exchanges are expected to increase, due to enhanced continental erosion (notably through permafrost thawing and increased river flow). These changes are driven by climate and in turn impact the climate. This study aims at assessing possible shifts in oceanic circulation and particle fluxes resulting from these climate-driven changes in the Amerasian Basin of the Arctic Ocean, during the last few decades. To achieve this goal, we measured geochemical tracers of circulation and particle fluxes in seawater samples collected in this area between 2005 and 2015, which we compared to published data from samples collected between 1983 and 2000. The primary geochemical tracers studied here are 230 Th and 231 Pa. These radioisotopes are uniformly produced in seawater, from uranium decay, and are strongly reactive with particles. Therefore, their oceanic distribution depends on particle fluxes and circulation. The evolution of their distribution in the Amerasian Basin over space and time documents enhancement of particle flux and lateral mixing in the Amerasian basin of the Arctic Ocean over the last three decades. Key Points: • Concentration decreases of 230 Th d and 231 Pa d suggest an enhancement of particulate scavenging since the 2000s in the Amerasian Basin • Particulate scavenging results from higher productivity and sediment resuspension from the shelves • Post-2...

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Section: Lateral Exchanges In Other Areas Of the Amerasian Basin 54contrasting

confidence: 99%

Changes in Circulation and Particle Scavenging in the Amerasian Basin of the Arctic Ocean over the Last Three Decades Inferred from the Water Column Distribution of Geochemical Tracers

et al. 2019

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“…Both an approximate heat budget (Timmermans et al 2003;Carmack et al 2012) and an overturn analysis of the interfaces (Timmermans et al 2003) indicate that F H is less than that predicted using the parameterization of Kelley (1990), however, it is not known by exactly how much. Both an approximate heat budget (Timmermans et al 2003;Carmack et al 2012) and an overturn analysis of the interfaces (Timmermans et al 2003) indicate that F H is less than that predicted using the parameterization of Kelley (1990), however, it is not known by exactly how much.…”

Section: Oceanic Implicationsmentioning

confidence: 95%

“…A number of previous studies in polar regions have speculated on staircases in which the heat fluxes appear to be significantly less than the laboratory-derived laws (Howard et al 2004;Timmermans et al 2003;Polyakov et al 2012;Carmack et al 2012). A number of mechanisms may be important for the observed flux reduction, such as a mean shear present across the interfaces (Polyakov et al 2012) or lateral effects (Kelley et al 2003).…”

Section: Oceanic Implicationsmentioning

confidence: 95%

“…Such conditions are often found to exhibit a double-diffusive staircase in which the water column forms a series of homogeneous mixed layers where small-scale convective mixing is taking place, separated by relatively thinner densitystratified interfaces (Fig. For example, temperature interface thicknesses h have been reported to have a range of 0.05 # h # 20 m, with jumps in temperature of 0.001 # DT # 0.58C, leading to heat flux estimates of 0.02 # F H # 10 W m 22 Dillon 1987, 1989;Timmermans et al 2003Timmermans et al , 2008Polyakov et al 2012;Carmack et al 2012;Sirevaag and Fer 2012). We shall restrict ourselves to the diffusive regime, where the heat fluxes that result from DDC have been suggested to be an important contribution to the upper-ocean heat budget of the Arctic Ocean (e.g., Polyakov et al 2012;Turner 2010).…”

Section: Introductionmentioning

confidence: 99%

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Does Rotation Influence Double-Diffusive Fluxes in Polar Oceans?

Carpenter

Timmermans

2014

Journal of Physical Oceanography

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The diffusive (or semiconvection) regime of double-diffusive convection (DDC) is widespread in the polar oceans, generating ''staircases'' consisting of high-gradient interfaces of temperature and salinity separated by convectively mixed layers. Using two-dimensional direct numerical simulations, support is provided for a previous theory that rotation can influence DDC heat fluxes when the thickness of the thermal interface sufficiently exceeds that of the Ekman layer. This study finds, therefore, that the earth's rotation places constraints on small-scale vertical heat fluxes through double-diffusive layers. This leads to departures from laboratory-based parameterizations that can significantly change estimates of Arctic Ocean heat fluxes in certain regions, although most of the upper Arctic Ocean thermocline is not expected to be dominated by rotation.

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“…In 1969, Neal et al already found strong layering structures suggestive double-diffusive convection in abyssal AO. It was supposed to be the major attribution of the thermocline intrusions in the AO (May and Kelley, 2002), which was responsible for the climate changes of the arctic in recent decades (Carmack et al, 1997(Carmack et al, , 2012. Moreover, due to the possible effect in the formation of the northern water masses, the double-diffusive convection might be an important factor of the global climate system.…”

Section: Introductionmentioning

confidence: 97%

Observational analysis of the double-diffusive convection in the deep Canada Basin

Xie

2015

Acta Oceanol. Sin.

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The Canada Basin (CB) is the largest sub-basin in the Arctic, with the deepest abyssal plain of 3 850 m. The double-diffusive process is the possible passage through which the geothermal energy affects the above isolated deep waters. With the temperature-salinity-pressure observations in 2003, 500-m-thick transition layers and lower 1 000-m-thick bottom homogenous layers were found below 2 400 m in the central deep CB. Staircases with downward-increasing temperature and salinity are prominent in the transition layers, suggesting the doublediffusive convection in deep CB. The interface of the stairs is about 10 m thick with 0.001-0.002°C temperature difference, while the thicknesses of the homogenous layers in the steps decrease upward from about 60 to 20 m. The density ratio in the deep central CB is generally smaller than 2, indicating stronger double-diffusive convection than that in the upper ocean of 200-400 m. The heat flux through the deepest staircases in the deep CB varies between 0.014 and 0.031 W/m 2 , which is one-two orders smaller than the upper double-diffusive heat flux, but comparable to the estimates of geothermal heat flux. Citation: Xie Lingling, Li Mingming, Li Min. 2015. Observational analysis of the double-diffusive convection in the deep Canada Basin.

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The Arctic Ocean warms from below

Cited by 30 publications

References 33 publications

Changes in Circulation and Particle Scavenging in the Amerasian Basin of the Arctic Ocean over the Last Three Decades Inferred from the Water Column Distribution of Geochemical Tracers

Changes in Circulation and Particle Scavenging in the Amerasian Basin of the Arctic Ocean over the Last Three Decades Inferred from the Water Column Distribution of Geochemical Tracers

Does Rotation Influence Double-Diffusive Fluxes in Polar Oceans?

Observational analysis of the double-diffusive convection in the deep Canada Basin

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