McMurdo Ice Shelf, Antarctica

Ice shelf surface

The McMurdo Ice Shelf is one of the most unusual in Antarctica. In addition to large areas covered by snow, there are also areas of pale blue glacier ice and darker marine ice. The bare ice areas are heavily pitted. The marine ice accretes to the base of the ice shelf, and as the surface melts off, so this ice gradually works its way to the surface, bringing with it sediment and organisms. There are extensive areas of debris cover and numerous meltwater channels. The ice shelf edge is characterised by intricate carving and gullying of the ice. Summer melt had not really begun in ernest during our early summer visit.

Ice shelf surface
The rough, pitted surface of the McMurdo Ice Shelf near the camp is overlooked by Mt Discovery, where a strong southerly wind is whipping up spindrift around the summit.
Ice shelf surface
Hard ice surface of the ice shelf, reflecting the sun, looking towards Black Island. A few patches of snow remain in this area.
Ice shelf surface
Sastrugi (wind-generated snow dunes) near the camp. They are orientated in the direction of the prevailing southerly wind.
Ice shelf surface
Wind ripples formed transverse to the prevailing southerly wind on refrozen water ice. Their form is enhanced by recent snow.
Ice shelf surface
Snow-covered part of the ice shelf, close to where it impinges against Ross Island.
Ice shelf surface
Wind-scoured snow, barely sastrugi, on the ice shelf, with Mt Erebus in the background.
Ice shelf surface
Tractors follow a route through the gap between Black Island and White Island, marked by bamboo poles. In the background is Mt Erebus.
Ice shelf surface
The main accumulation zone on the ice shelf, looking towards White Island. This area is close to sea level, but receives more snow than other parts of the ice shelf.
Ice shelf surface
Small un-named glacier, flowing off Black Island into McMurdo Ice Shelf.
Ice shelf surface
Looking down on the McMurdo Ice Shelf from Minna Bluff, showing the longitudinal ridges and rough bare ice surface of the marginal zone of the ice shelf.
Ice shelf surface
The amount of snow precipitation adjacent to Minna Bluff is tiny. During blizzards, most of the snow is transferred away, leaving starved ripples on a bare ice surface.
Ice shelf surface
A pair of unusual starved ripples resting on a surface of marine ice.
Ice shelf surface
A ‘snow snake’, resulting from localised snow deposition on the ice surface. It trends parallel to the wind direction.
Ice shelf surface
Some hollows in the ice surface collect more substantial deposits of snow. Here are some fresh snow dunes.
Ice shelf surface
Detail of snow dunes, showing the granular texture of the wind-blown snow.
Ice shelf surface
Deep channel cut into marine ice and capped by glacier ice, close to southern margin of ice shelf; Black Island in the background.
Ice shelf surface
Accretion layering at the surface of the ice shelf just off Minna Bluff. This is the result of marine ice forming at the base of the ice shelf in stages. Boundaries are commonly marked by marine fossils.
Ice shelf surface
Accretion layering in marine ice. The trekking pole indicates that each layer is typically 1 to 2 metres thick. Refrozen water ice is in the foreground.
Ice shelf surface
Marine ice has a unique layered structure. The layers are typically lens-shaped and bounded by air bubbles. They form approximately vertical to the main accretion layers, and superficially resemble foliation in glacier ice.
Ice shelf surface
A cylindrical cryoconite hole approximately 15 cm in diameter. Water overlies a film of debris and algae, but is capped by a lid of ice.
Ice shelf surface
Cryoconites come in many shapes and sizes; this one is oval-shaped.
Ice shelf surface
Turquoise refrozen water ice in frozen streams and ponds contrasts strongly with the greyish marine ice near the southern ice shelf boundary at Minna Bluff.
Ice shelf surface
Blue water ice close up with Mt Dicovery in the background.
Ice shelf surface
Water on freezing expands, forming prominent ‘ice blisters’, which are mounds with cracks across the top. These blisters usually form in confined stream courses.
Ice shelf surface
Turquoise blue ice ponds collect at the southern margin of the ice shelf, adjacent to Minna Bluff (in the background).
Ice shelf surface
Close up of etched ice crystals (candle ice) in plan view. When meltwater refreezes, vertical crystals up to 30 cm long form, which when weathered can be demolished into their constituent ‘candles’.
Ice shelf surface
A vertical dyke of blue clear ice several metres wide near the margin of the ice shelf at Minna Bluff. Clearly a fracture that was originally water-filled, the actual origin of this feature is a puzzle.
Ice shelf surface
Close-up of clear fractured ice in the middle of the dyke.
Ice shelf surface
Truncated frozen water-filled former crevasse near a prominent medial moraine that extends into the ice shelf from the shore of Minna Bluff.
Ice shelf surface
A set of narrow parallel frozen water-filled crevasses, near the prominent medial moraine.
Ice shelf surface
An intricately carved, 3 m high, ice wall in a channel near the shore of Minna Bluff, formed from a combination of water erosion and ablation.
Ice shelf surface
Details of miniature buttresses, ice texture and marine ice layering in the same channel wall.
Ice shelf surface
Scalloped sliver of ice a metre or so wide on the wall of a meltwater channel.
Ice shelf surface
Anastomosing marine ice ridges with intervening channels near the ice shelf margin at Minna Bluff. The relief is several metres.
Ice shelf surface
Swaley ice topography of several metres relief at the ice shelf margin. This is another telephoto view, but with Black Island in the background.
Ice shelf surface
A solitary figure descends an ice ridge onto the wind-polished water-ice close to the ice margin at Minna Bluff.
Ice shelf surface
An undercut channel water displaying inclined accretion layering within marine ice in the vicinity of the medial moraine extending from Minna Bluff.
Ice shelf surface
Erosion by stream channels has left this striking leaning ice tower.
Ice shelf surface
The overhanging wall of a meltwater channel reveals these delicate icicles.
Ice shelf surface
Looking up at the sky from underneath the roof of the overhang shows a sparkling set of icicles.
Ice shelf surface
A wind-rippled snow surface in the middle of the ice shelf is draped with beautiful sparkling "ice flowers", some of which are reflecting the sun.
Ice shelf surface
A near-horizontal layer of debris emerging from the marine ice zone of the ice shelf near Minna Bluff. This debris represents a sample of the sea floor that originally froze to the bottom of the ice shelf.
Ice shelf surface
Sean Fitzsimons using a chain saw to collect ice blocks for isotopic analysis. The results will convey information about the origin of the ice.
Ice shelf surface
High-resolution ground-penetrating radar surveying on foot with Mt Discovery in the background. The results show the internal layering of the ice shelf.
Ice shelf surface
Radar surveying by dragging the instruments at low speed using the Hägglunds.
Ice shelf surface
Fractures in marine ice at the ice shelf surface, picked out by fresh wind-blown snow.
  
Photos Michael Hambrey, November and December 2010.