Horizontal Density Structure and Restratification of the Arctic Ocean Surface Layer

Timmermans, Mary‐Louise; Cole, Sylvia T.; Toole, John M.

doi:10.1175/jpo-d-11-0125.1

Cited by 95 publications

(110 citation statements)

References 30 publications

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“…Arctic SCVs isolate and transport anomalous water properties, and have implications for transport and lateral dispersion in the Arctic. Furthermore, Timmermans et al (2012) observe restratification in the upper layers that can be attributed to lateral processes associated with sub-mesoscale features. This has consequences for maintaining the insulating stratification of the CHL.…”

Section: Sub-mesoscale Eddies Fronts and Other Processesmentioning

confidence: 90%

“…In addition, efficient lateral mixed-layer restratification also impedes mixed-layer deepening . Re-stratification as a result of sub-mesoscale (order of 1 km) instabilities within the surface layer is reported using ice-tethered profiler measurements from the Canada Basin (Timmermans et al, 2012). Previous and subsequent estimates of vertical diffusivity and heat transport therefore suggest that the warm subsurface layers in the central basins cannot contribute to significant ice melt.…”

Section: Diapycnal Mixing In the Arctic Oceanmentioning

confidence: 93%

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Advances in understanding and parameterization of small-scale physical processes in the marine Arctic climate system: a review

et al. 2014

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Abstract. The Arctic climate system includes numerous highly interactive small-scale physical processes in the atmosphere, sea ice, and ocean. During and since the International Polar Year 2007-2009, significant advances have been made in understanding these processes. Here, these recent advances are reviewed, synthesized, and discussed. In atmospheric physics, the primary advances have been in cloud physics, radiative transfer, mesoscale cyclones, coastal, and fjordic processes as well as in boundary layer processes and surface fluxes. In sea ice and its snow cover, advances have been made in understanding of the surface albedo and its relationships with snow properties, the internal structure of sea ice, the heat and salt transfer in ice, the formation of superimposed ice and snow ice, and the small-scale dynamics of sea ice. For the ocean, significant advances have been related to exchange processes at the ice-ocean interface, diapycnal mixing, double-diffusive convection, tidal currents and diurnal resonance. Despite this recent progress, some of these small-scale physical processes are still not sufficiently understood: these include wave-turbulence interactions in the atmosphere and ocean, the exchange of heat and salt at the ice-ocean interface, and the mechanical weakening of sea ice. Many other processes are reasonably well understood as stand-alone processes but the challenge is to understand their interactions with and impacts and feedbacks on other processes. Uncertainty in the parameterization of small-scale processes continues to be among the greatest challenges facing climate modelling, particularly in high latitudes. Further improvements in parameterization require new year-round field campaigns on the Arctic sea ice, closely combined with satellite remote sensing studies and numerical model experiments.

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Section: Sub-mesoscale Eddies Fronts and Other Processesmentioning

confidence: 90%

Section: Diapycnal Mixing In the Arctic Oceanmentioning

confidence: 93%

Advances in understanding and parameterization of small-scale physical processes in the marine Arctic climate system: a review

et al. 2014

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“…This has been observed in warm regions such as the Tyrrhenian Sea in the Mediterranean [2,3] and in the western Atlantic near the Caribbean Sea [4][5][6]. Recent observations have also shown that density staircases persist over large regions of the Arctic Ocean [7][8][9][10]. It is this case that is of particular interest because the reduction in sea ice in recent years has resulted in enhanced generation of internal gravity waves (or internal waves, for short) [11,12].…”

Section: Introductionmentioning

confidence: 94%

Internal wave transmission through a thermohaline staircase

Sutherland

2016

Phys. Rev. Fluids

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With the aim to predict energy transport by internal waves incident upon observed density staircases in the ocean, the theory for internal wave tunneling through a single finite-size mixed region is extended to predict the transmission of internal waves through a piecewise-constant density profile with an arbitrary number of steps. An analytic solution is found if all steps have equal vertical extent. From this solution, bounds are established for the relative incident horizontal wave number and frequency of waves that have negligible transmission, a result that is independent of the number of steps. If the step sizes vary randomly about a mean vertical extent, the transmission can be computed numerically for several random realizations. Provided the horizontal wavelength is much longer than the total vertical extent of the staircase, the standard deviation of the computed transmission coefficients is small and the mean agrees well with the analytic prediction for equally spaced steps. The results are applied to thermohaline staircases observed in the ocean in order to put lower bounds on the wavelengths of long inertia gravity waves that significantly transmit to great depth.

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“…Drift speeds were ~ 10 km day -1 , limiting observations to a largely temporal view of the upper ocean. Previous work by Timmermans et al (2012) show that the Canada Basin surface mixed layer can have significant horizontal density gradients during the winter season; however, the findings of Gallaher et al (2016) indicate remarkable regional consistency in salinity and temperature profiles across the upper 50 m of the ocean during the summer season (see Figure 15 of Gallaher et al, 2016). Heat budgets conducted during this study closed to within about 10%, suggesting that lateral advections were very low and that the bulk of upper ocean heat storage gains and basal ice melt were achieved by absorption of local shortwave radiative input.…”

Section: One-dimensional Analysis Of Nstmsmentioning

confidence: 99%

Field observations and results of a 1-D boundary layer model for developing near-surface temperature maxima in the Western Arctic

Gallaher

Stanton

Shaw

et al. 2017

Elementa: Science of the Anthropocene

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Gallaher, SG et al 2017 Field observations and results of a 1-D boundary layer model for developing near-surface temperature maxima in the Western Arctic. Elem Sci Anth, 5: 11, pp. 1-21, DOI: https://doi.org/10.1525/elementa.195 IntroductionRecent changes in the Arctic ice-ocean system have led to an increase in upper ocean heating. The primary source of this heating is the two-fold rise in ocean-absorbed solar radiation (Perovich et al., 2007) that results from rapidly declining summer sea ice extent (Comiso et al., 2008;Steele et al., 2010). Recent studies in the Canada Basin show that this absorbed solar heating is partitioned 0.23/0.77 between ocean heat storage and latent heat loss (basal ice melt), respectively (Toole et al., 2010;Gallaher et al., 2016). Most of the oceanic heat is accumulated in near-surface temperature maximum (NSTM) features. The NSTM is defined as an upper ocean (< 50 m) temperature maximum that: 1) is at least 0.2°C above freezing (δT); 2) has a salinity < 31; and 3) resides above a cooler water layer by at least 0.1°C (Jackson et al., 2010). Jackson et al. (2010) attribute NSTM development to the absorption of solar radiation in shallow, stratified layers beneath melting sea ice and open water during summer. Steele et al. (2011) present an additional formation process caused by cooling of the near-surface ocean under open water areas in late summer, which leaves behind a warmer subsurface layer. Although NSTM heat is gained in the summer, the release of this heat often occurs in later seasons. Observations in the Canada Basin show that the NSTM often survives into fall, and that heat from this layer can be mixed into the surface mixed layer to delay or slow freeze up (Steele et al., 2008;Jackson et al., 2010;Steele et al., 2011;Timmermans, 2015).Early studies of the NSTM during AIDJEX (Maykut and McPhee, 1995) and SHEBA (McPhee et al., 1998) found that the layer was present directly below the summer surface mixed layer, at depths between 25 and 35 m. However, the Canada Basin upper ocean is freshening (McPhee et al., 2009) Summer sea ice extent in the Western Arctic has decreased significantly in recent years resulting in increased solar input into the upper ocean. Here, a comprehensive set of in situ shipboard, on-ice, and autonomous ice-ocean measurements were made of the early stages of formation of the near-surface temperature maximum (NSTM) in the Canada Basin. These observations along with the results from a 1-D turbulent boundary layer model indicate that heat storage associated with NSTM formation is largely due to the absorption of penetrating solar radiation just below a protective summer halocline. The depth of the summer halocline was found to be the most important factor for determining the amount of solar radiation absorbed in the NSTM layer, while halocline strength controlled the amount of heat removed from the NSTM by turbulent transport. Observations using the Naval Postgraduate School Turbulence Frame show that the NSTM was able to persist despite periods of i...

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Horizontal Density Structure and Restratification of the Arctic Ocean Surface Layer

Cited by 95 publications

References 30 publications

Advances in understanding and parameterization of small-scale physical processes in the marine Arctic climate system: a review

Advances in understanding and parameterization of small-scale physical processes in the marine Arctic climate system: a review

Internal wave transmission through a thermohaline staircase

Field observations and results of a 1-D boundary layer model for developing near-surface temperature maxima in the Western Arctic

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