Upwelling by icebergs

Neshyba, Steve

doi:10.1038/267507a0

Cited by 59 publications

(38 citation statements)

References 3 publications

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“…Instead, meltwater emerges to the surface, mixing with the adjacent marine water. Iceberg melting with resultant upwelling was calculated first by Neshyba [1977] in the Weddell Sea, followed by laboratory experiments [Huppert and Josberger, 1980] It has been shown that glacial particles aggregate rapidly when released into the sea water [Hoskin and Burrell, 1972]. Our study confirmed this result directly by comparing in situ particle size distribution measurements using a photographic …”

Section: Mechanisms For Inl Formation and Settling Of Aggregated Finesupporting

confidence: 77%

Influence of melting icebergs on distribution, characteristics and transport of marine particles in an East Greenland fjord

Azetsu-Scott¹,

Syvitski²

1999

J. Geophys. Res.

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Abstract. A detailed study of distribution of suspended sediments in an East Greenland fjord with a high iceberg production rate reveals the existence of intermediate nepheloid layers (INLs).Observed INLs extended from the head to the mouth of the fjord at water depths between 100 and 400 m. Particulate organic carbon and nitrogen, chlorophyll a, and nutrient measurements and observation by microscope and energy dispersive X-ray analyses were used to characterize marine particles. Particles in the INLs are composed of glacial flour including >50 •tm quartz and feldspar grains with angular and sharp edges, considered to be released from melting icebergs. In situ photographs show large aggregates (> 1 mm) at high concentration (>300 particles per liter) in and below INLs. These aggregates, in comparison with the dispersed particle size distribution, demonstrate that smaller size particles (e.g., clay) settle effectively along with larger single size grains. In Kangerlugssuaq Fjord, the mass transport of marine particles was governed by the subsurface iceberg melting, producing observed INLs, rather than the surface meltwater plume. This suggests that the subsurface water temperature controls release of iceberg debris and the existence of warm subsurface water, as well as the spread of cold and fresh water in the surface layer, needs to be considered to evaluate the occurrence of ice-rafted debris layers, including Heinrich layers. This study provides the field evidence of a modem analogue on ocean conditions that could form iceberg-rafted layers.

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Section: Mechanisms For Inl Formation and Settling Of Aggregated Finesupporting

confidence: 77%

Influence of melting icebergs on distribution, characteristics and transport of marine particles in an East Greenland fjord

Azetsu-Scott¹,

Syvitski²

1999

J. Geophys. Res.

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“…Those results are consistent with the convection of warm water near icebergs [Neshyba, 1977] in the Antarctic and penetration of the Atlantic water heat to the upper layer of the Arctic Ocean through transient apertures in the pycnocline.…”

Section: Introductionsupporting

confidence: 78%

Characteristics of the meltwater field from a large Antarctic iceberg using

et al. 2015

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Large tabular icebergs represent a disruptive influence on a stable water column when drifting in the open ocean. This is a study of one iceberg, C18A, encountered in the Powell Basin in the Weddell Sea in March 2009, formed from iceberg C18 ( 76×7 km) originating from the Ross Ice Shelf in May 2002. C18A was lunate in shape with longest dimensions of 31 km×7 km×184 m. The meltwater field from C18A was characterized using δ18O from water samples collected near C18A (Near‐field, 0.4–2 km) and contrasted with a Far‐field comprised of samples from an Away site (19 km from C18A), a Control site (70 km away), and a region populated with small icebergs (Iceberg Alley, 175 km away). The in‐sample fractions of meteoric water were calculated relative δ18O in iceberg ice and Weddell Deep Water and converted to meteoric water height (m) and a percentage within 100 m depth bins. The Near‐field and Far‐field difference from surface to 200 m was 0.51±0.28%. The concentration of meteoric water dropped to approximately half that value below 200 m, approximate keel depth of the iceberg, although detectable to 600 m. From surface to 600 m, the overall difference was statistically significant ( P<0.0001). From this, we estimate the Near‐field volume astern of the iceberg ( 0.16 km3normald−1) as a continuous source of meteoric water.

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“…All the experiments were viewed using the shadowgraph technique, and in some of these up to six layers of dye were introduced into the water a t different levels during the filling process. The purpose of the dye was to allow us to ascertain the transport and final position of the ambient water, and in particular to test the prediction of Neshyba (1977) that large amounts of ambient water would be entrained in a rising turbulent boundary layer. For some experiments a minute quantity of fluorescein was frozen uniformly into the ice block.…”

Section: Melting Ice In a Salinity Gradientmentioning

confidence: 99%

Ice blocks melting into a salinity gradient

1980

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I n our previous qualitative paper, it was shown that when a vertical ice surface melts into a stable salinity gradient, the melt water spreads out into the interior in a series of nearly horizontal layers. The experiments reported here are aimed a t quantifying this effect, which could be of some importance in the application to melting icebergs. Experiments have also been carried out with heated and cooled vertical walls a t larger Rayleigh numbers R than those of previous experiments.The main result is that for most of our experiments there is no significant difference between these three cases when properly scaled. The layer thickness over a wide range of R is described to within the experimental accuracy by where the term in brackets is the horizontal buoyancy difference evaluated a t the mean salinity and dpldz is the vertical density gradient due to salinity. I n the case of ice melting into warm water the effective wall temperature T, is approximately 0 "C, whereas in colder water the freezing point depression must be taken explicitly into account. A detailed examination of the vertically flowing inner melt water layer in both homogeneous and salinity stratified cases has been made. This layer and the melt water which is mixed outwards from it into the turbulent horizontal layers have little effect on the outer flow. At high R and large external salinity, however, mixing can reduce the effective salinity a t the inner edge of the horizontal layers, and thus the layer scale. A puzzling feature is the relatively weak dependence of layer scale on local salinity, though the vigour of convection and the rate of melting are greater where the salinity is high.The direct application of our results to oceanographic situations predicts layer scales under typical summer conditions of order tens of metres in the Antarctic and of order metres in the Arctic. More measurements will be needed, especially close to icebergs, before the application of these ideas to polar regions can be properly evaluated.

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Upwelling by icebergs

Cited by 59 publications

References 3 publications

Influence of melting icebergs on distribution, characteristics and transport of marine particles in an East Greenland fjord

Influence of melting icebergs on distribution, characteristics and transport of marine particles in an East Greenland fjord

Characteristics of the meltwater field from a large Antarctic iceberg using

Ice blocks melting into a salinity gradient

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