The Physical Processes involved in the Melting of Icebergs (Invited paper)

Huppert, Herbert E.

doi:10.3189/s0260305500017067

Cited by 19 publications

(20 citation statements)

References 16 publications

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“…Melting of vertical ice walls in the ocean has been discussed by Gill (1973), , Gade (1979), Greisman (1979), Huppert (1980), andRussell-Head (1980). These give a range of melt-rates which bracket the rates presented here.…”

mentioning

confidence: 54%

Evolution of under Water Sides of Ice Shelves and Icebergs

Orheim

1987

A. Glaciology.

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A systematic programme of side-scan sonar and plumbline soundings was carried out in the Weddell Sea area in 1985 to measure the under-water sides of ice shelves and icebergs. From these observations the following model is suggested for the evolution of the ice front:(1) Initial stage: fracturing of the ice shelves takes place along smooth, curvi-linear segments with vertical faces. (2) Formative stage:the freshly formed vertical face is eroded both by wave and swell action around the water line, by small calvings from the undercut, overhanging subaerial face, and by submarine melting. The melting has a minimum at 50-100 m depth, and increases with depth to a rate of around 10 m a-I at 200 m. This is about twice the rate of erosion at the water line. The vanatlOn in melting with depth results from a combination of summer melting by near-surface water, and year-round melting by water masses that are increasingly warmer than the pressure melting-point with depth. (3) Mature stage: this stage is reached after a few years of exposure. The backward erosion of the face leads to a shape with a prominent under-water "nose" with a maximum projection to more than 50 m at 50-100 m depth. The ramp above this slopes upwards to meet the vertical wall about 5 m below the water line. The ice below the nose is melted back beyond the above-water face. There is no net buoyancy and ice shelves at this mature stage are generally 1101 up-warped at the front . INTRODUCTIONThis paper discusses the evolution of the front of ice shelves and the sides of icebergs, with main emphasis on changes below the water line.Ice shelves float, and are modified in contact with seawater. A freshly calved tabular iceberg is a sample of the ice shelf, with the experimental advantage of including sides that have not been affected by the sea, and at least one side that has been exposed for some time.The shapes and the physical dimensions of ice fronts tend to be similar around Antarctica. This, and the opportunity of recognizing ice fronts and icebergs recently calved, gives good conditions for systematic studies of the evolution of the free faces. Furthermore, ice fronts can sometimes be observed to have moved steadily outwards without undergoing large-scale calving. Such locations are especially attractive for investigation of changes with time.A typical ice-shelf front is around 200 m high, of which 30-35 m is above water. The free board is greater than for pure ice because the ice shelves consist of firn in their upper layers. The elevation of the ice front generally varies little over short distances, except where grounding has taken place. Our typical measurements show a height of freeboard within 28 ± 4 m over a distance of several kilometres.The map shape shown by the ice front is partly a question of scale.It will generally appear straight or slightly curved on a scale of a kilometre or less.The curved segments have the concave side to the sea, i.e. the fracture lines meet in cusps pointing away from the ice

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mentioning

confidence: 54%

Evolution of under Water Sides of Ice Shelves and Icebergs

Orheim

1987

A. Glaciology.

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“…For a complete treatment, see Bigg (2016). Despite the relatively warm observed air temperatures during the study period (Figure 3A), surface melt due to atmospheric fluxes was likely negligible compared to subsurface melt (Huppert, 1980). Sublimation was probably negligible due to prevailing humid conditions ( Figure 3B).…”

Section: Bergy Bit Dynamics and Thermodynamicsmentioning

confidence: 99%

“…Equations 10-12 do not account for temporal variability of parameters such as wave height and, therefore, is valid only for a sufficiently short period of time (e.g., t ≈ 1 day). Wave erosion has been suggested as the dominant process responsible for iceberg mass loss (Huppert, 1980;Savage et al, 2001). In the inner fjord, where ice abundance is high, waves are small due to limited fetch and the dampening effect of the ice.…”

Section: Bergy Bit Dynamics and Thermodynamicsmentioning

confidence: 99%

Bergy Bit and Melt Water Trajectories in Godthåbsfjord (SW Greenland) Observed by the Expendable Ice Tracker

et al. 2017

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Icebergs and bergy bits makes up a significant component of the total freshwater flux from the Greenland Ice Sheet to the ocean. Observations of iceberg trajectories are biased toward larger icebergs and, as a result, the drift characteristics of smaller icebergs and bergy bits are poorly understood. In an attempt to fill this critical knowledge gap, we developed the open-source EXpendable Ice TrackEr (EXITE). EXITE is a low-cost, satellite-tracked GPS beacon capable of high-resolution temporal measurements over extended deployment periods (30 days or more). Furthermore, EXITE can transform to a surface drifter when its host iceberg capsizes or fragments. Here we describe basic construction of an EXITE beacon and present results from a deployment in Godthåbsfjord (SW Greenland) in August 2016. Overall, EXITE trajectories show out-fjord surface transport, in agreement with a simple estuarine circulation paradigm. However, eddies and abrupt wind-driven reversals reveal complex surface transport pathways at time scales of hours to days.

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“…This progressively leads to the formation of a projecting ramp which is subject to buoyancy-induced calving. Ramp formation is further promoted by the fact that melt rates decrease with increasing water pressure at depth (Huppert 1980). By contrast, a lower waterline melt rate will lead to a slower retreat rate of the subaerial ice cliff, and this could allow the subaerial and submerged parts of the cliff to retreat at similar rates, inhibiting ramp formation.…”

Section: Lake Geometrymentioning

confidence: 99%

Temperature and bathymetry of ice‐contact lakes in Mount Cook National Park, New Zealand

Warren¹,

Kirkbride²

1998

New Zealand Journal of Geology and Geophysics

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Several ice-contact lakes have formed in conjunction with twentieth century glacier retreat in Mt Cook National Park. They occupy overdeepened glacial valleys and are dammed by terminal moraines and/or outwash heads. During the autumns of 1994 and 1995, the temperature and bathymetry of "Maud lake", "Godley lake", and Hooker Lake were surveyed. The near-glacier vertical water temperature profiles exhibited greater temperature variation than those at the distal ends of the lakes. Thermal stratification existed in Hooker Lake, whereas both Maud and Godley lakes were thoroughly mixed. Water temperatures in the latter were consistently between 3 and 4.5°C, but most parts of Hooker Lake were cooler than 2°C, with a minimum recorded temperature of 0.2°C. These contrasts are important because melting of submerged parts of glacier termini is significant for ablation rates and for the dynamics of calving termini. All the lakes are steep sided and deep. Maud and Godley lakes approach 100 m in depth, whereas Hooker Lake has a maximum recorded depth of 136 m. Extensive flat floors in Maud and Godley lakes probably reflect rapid sediment accumulation following glacier retreat. Water depth at the termini of iceberg-calving glaciers is known to correlate strongly with rates of iceberg production and hence the rate of glacier retreat. However, given the substantial water depths through which these glaciers (and also the neighbouring Tasman Glacier) have retreated, they appear to be more stable than comparable glaciers in other countries. The subaqueous geometry of all the glacier termini comprises a projecting ramp of glacier ice. All the lakes are being enlarged by glacier retreat except Maud lake, which has been reduced in size since 1995 by the advance of Maud and Grey Glaciers.

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The Physical Processes involved in the Melting of Icebergs (Invited paper)

Cited by 19 publications

References 16 publications

Evolution of under Water Sides of Ice Shelves and Icebergs

Evolution of under Water Sides of Ice Shelves and Icebergs

Bergy Bit and Melt Water Trajectories in Godthåbsfjord (SW Greenland) Observed by the Expendable Ice Tracker

Temperature and bathymetry of ice‐contact lakes in Mount Cook National Park, New Zealand

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