Non-linear thermal transport and brine convection in first-year sea
                  ice

McGuinness, Mark; Trodahl, H. J.; Collins, Katie S.; Haskell, T. G.

doi:10.3189/s0260305500017924

Cited by 16 publications

(55 citation statements)

References 11 publications

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“…In this paper we present results from a program started in the mid‐1990s to measure the thermal conductivity of sea ice using arrays of thermistor strings frozen into landfast ice. In previously published findings from this program, which we have now concluded, three departures from the expected behavior were observed [ McGuinness et al , 1998; Trodahl et al , 2000, 2001]: (1) A conductivity reduction of 25–50% was resolved over the top 50 cm of first‐year (FY) ice. (2) Below these depths, an overall reduction of 10% was observed compared with effective‐medium predictions.…”

Section: Introductionmentioning

confidence: 87%

Thermal conductivity of landfast Antarctic and Arctic sea ice

et al. 2007

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[1] We present final results from a program to measure the thermal conductivity of sea ice with in situ thermistor arrays using an amended analysis of new and previously reported ice temperatures. Results from landfast first-year (FY) ice near Barrow, Alaska, and McMurdo Sound, Antarctica, are consistent with predictions from effective-medium models but 10-15% higher than values from the parameterization currently used in most sea ice models. We observe no previously reported anomalous near-surface reduction, which is now understood to have been an artifact, nor a convective enhancement to the heat flow, although our analysis is limited to temperatures below À5°C at which brine percolation is restricted. Results for landfast multiyear (MY) ice in McMurdo Sound are also consistent with effective-medium predictions, and emphasize the density dependence. We compare these and historical measurements with effective-medium predictions and the representation commonly used in sea ice models, developed originally for MY Arctic ice. We propose an alternative expression derived from effective-medium models, appropriate for both MY and FY ice that is consistent with experimental results, k = (r/r i )(2.11 À 0.011 q + 0.09 (S/q) À (r À r i )/1000), where r i and r are the density of pure ice and sea ice (kg m À3 ), and q (°C) and S (ppt) are sea ice temperature and salinity. For the winter and spring conditions studied here, thermal signatures of internal brine motion were observed rarely (22 times in 1957 days), and their maximum contribution to the total heat flow is estimated to be of the order of a few percent.

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Section: Introductionmentioning

confidence: 87%

Thermal conductivity of landfast Antarctic and Arctic sea ice

et al. 2007

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“…We use a graphical finite difference scheme, which we have previously applied to sea ice measurements [ McGuinness et al , 1998; Trodahl et al , 2000, 2001], that does not require harmonic forcing and is insensitive to interthermistor calibration offsets. As for the other finite difference methods discussed in the preceding paragraph, we make the assumption of locally constant thermal properties for the space between adjacent thermistors.…”

Section: Analysis Methodsmentioning

confidence: 99%

“…The thermistor arrays are adapted from units custom‐built for measuring heat flow in first‐year sea ice [ McGuinness et al , 1998; Trodahl et al , 2000, 2001]. The body of the array is a 2‐m‐long, 0.25‐inch (6.35 mm) diameter, thin‐walled (0.2 mm) stainless steel tube.…”

Section: Instrumentation and Temperature Measurementsmentioning

confidence: 99%

Depth and seasonal variations in the thermal properties of Antarctic Dry Valley permafrost from temperature time series analysis

et al. 2003

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[1] We present the first dedicated study of the thermal properties of perennially frozen, ice-cemented, subsurface Dry Valley permafrost. From time series analysis of 14 months' temperature measurements, we resolve depth and seasonal variations in the thermal properties at two nearby sites at Table Mountain with different origin, composition, and polygonal ground patterning. We determine apparent thermal diffusivity (ATD) profiles directly from thermistor array measurements at 13.5-cm-depth intervals and 4-hour time intervals in the top 2 m. We treat the system as purely conductive year round due to the cold temperatures and compare the performance of several common analysis schemes with a graphical finite difference method that we present in detail. This comparison is facilitated by one site showing strong depth variations including an abrupt twofold increase in ATD across a sharp compositional boundary. We characterize the composition of the inhomogeneous ground from recovered cores and estimate an ice-fractiondependent heat capacity in the range C = 1.7 ± 0.1 to 1.8 ± 0.1 MJ m À3°CÀ1 . We calculate apparent thermal conductivity profiles that correlate very well with the core compositions. The conductivity generally lies in the range 2.5 ± 0.5 W m À1°CÀ1 but is as high as 4.1 ± 0.4 W m À1°CÀ1 for a quartose Sirius sandstone unit at one site. The seasonal variation in the ATD is consistent with its expected temperature dependence.

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“…The linear least squares fitting procedure underestimates the gradient when there are errors in the variable treated as independent (the x axis variable) [ Fuller , 1987]. In our case there are errors in both plotted variables and we have calculated the conductivity as the geometric mean of gradient estimates first treating ∂ zz T and then ρ∂ t U as the independent variable [ McGuinness et al , 1998; Trodahl et al , 2000]. This gives an unbiased estimate when the relative errors are the same in both variables but one that is biased downward if the relative uncertainties in ∂ zz T are larger than those in ρ∂ t U [ Fuller , 1987].…”

Section: Reexamining Analysis Of Array Measurementsmentioning

confidence: 99%

Direct measurement of sea ice thermal conductivity: No surface reduction

2006

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[1] We present new laboratory measurements of the thermal conductivity of small cores of landfast first-year (FY) and multiyear (MY) sea ice from McMurdo Sound, Antarctica. The conductivity of surface (0-10 cm) and subsurface (45-55 cm) FY ice, 2.14 ± 0.11 and 2.09 ± 0.11 W m -1 K -1, respectively, and MY surface ice, 1.88 ± 0.13 W m, are all consistent with effective medium predictions for measured salinity, density, and temperature. In contrast with a previous result from thermistor array measurements in FY ice, the present measurements in FY ice show no conductivity reduction over the top 50 cm. We have reexamined the analysis of these previous array measurements and have identified analytical effects that rendered this analysis unreliable in the presence of high-frequency surface temperature variations and pronounced surface warming and cooling events. We conclude that this apparent near-surface conductivity reduction was an artefact.

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Non-linear thermal transport and brine convection in first-year sea ice

Cited by 16 publications

References 11 publications

Thermal conductivity of landfast Antarctic and Arctic sea ice

Thermal conductivity of landfast Antarctic and Arctic sea ice

Depth and seasonal variations in the thermal properties of Antarctic Dry Valley permafrost from temperature time series analysis

Direct measurement of sea ice thermal conductivity: No surface reduction

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