Figure 1.
Envisat images showing the sea-ice conditions in late March around the West Ice shelf where two emperor colonies are located (equivalent imagery for 2009 is not available).
Darker areas denote poor sea-ice, grey shows thicker sea-ice and white indicates ice shelf. Note that the Barrier Bay colony has a permanent polynya while the West Ice shelf colony located on the sea-ice has thicker sea-ice at this time of year when the birds would be arriving in the area to breed (images courtesy of Polarview – www.polarview.aq).
Figure 2.
Shackleton Ice Shelf very high resolution satellite image.
WorldView2 image (15 September 2012) showing the location of the Shackleton Ice shelf colony in 2012 in context with the ice edge. On this image the four main sub-colonies are clearly visible on top of the Shackleton Ice Shelf around 5 km from the ice cliffs that form the edge of the ice shelf. The image data also clearly shows groups of penguins on their way to and from the ice edge, and the tracks they leave behind them. By marking these trails it is possible to assess where each group has come from and which direction it is heading. Interestingly at this site, the outgoing forages use a different route to the incoming penguins; on the way out they negotiate a large ice cliff. ICESAT data from the area suggest that the top of the ice sheet is 32–34 m high, the image shows no slope down to the cliff so the drop may be considerable (although there is evidence of large snowdrifts abutting the cliff). The incoming parties cannot negotiate the cliff and so take a 5 km longer route around the edge of the ice shelf until they can access the gentle slopes afforded by a number of ice creeks to the east of the colony. How the emperor penguins get down the ice cliff is, at present, unclear.
Figure 3.
Emperor penguins on the edge of the Larsen Ice Shelf near the Jason Peninsula late in the breeding season.
The larger group is on the ice-shelf, the smaller group has moved onto the fast-ice; earlier in the season data from QuickBird1 satellite imagery shows that the whole colony was located on the ice-shelf. Note the ice cliff which is probably an insurmountable barrier to the adult emperor penguins. No evident route to the colony was determined from the images. (Photo Ian Potten).
Figure 4.
A and B; maps showing location of the Jason Peninsula colony.
C: Quickbird1 image (12 Sept 2012) showing the main Jason Peninsula emperor penguin colony in relation to the ice-shelf and sea ice edge. D: Emperor penguins (small black dots) on their way to or from the breeding colony onto of the sea-ice. They have to climb up or down a small ice cliff, which shows up as white in this image. To the left of this cliff is ice shelf, while the ridged area to the right is fast-ice. In this image emperors can be seen on the ice shelf (a long line in upper left and parallel to the cliff face) and the cliff (shorter linear group at middle bottom and perpendicular to the cliff face). The height of this ice cliff is presently unknown but based on the size of the penguins in the image it may be only a few metres high.
Figure 5.
QuickBird 2 very high resolution satellite image of the Ruppert Coast emperor penguin colony(17 October 2012) including part of the Ruppert Coast and Nickerson Ice Shelf, it clearly shows the emperor penguin colony located on the higher ice shelf.
Access to the main colony seems to be by a shallow ice ramp north and west of the present location. Brown guano stains mark the previous colony site approximately half a kilometres northeast, and to the west, on the sea-ice is a smaller subgroup of penguins.
Figure 6.
Sea-ice concentration around the Shackleton Ice Shelf for the time period 2007 to 2012, each from the 20th of March.
White shading denotes thick sea-ice; blue, thinner sea-ice; black, open water. The red dot shows the location of the breeding colony identified from QuickBird VHR imagery (images courtesy of Polarview/University of Bremen).
Figure 7.
Histogram of three parameters at emperor penguin breeding colonies: blue bars represent mean March/April sea-ice concentration, red bars are latitude and green are mean temperature. Colonies are ranked from left to right with lowest sea-ice concentrations to the left. The four colonies mentioned in this paper are named in bold. Dashed lines in blue, red and green denote the mean of the three parameters for all colonies. Shackleton Ice shelf and Barrier Bay colonies are in locations that have the lowest mean autumn sea-ice concentrations. The Larsen ice shelf colony has slightly lower than average sea-ice concentrations, but its latitude and mean annual temperature are well above average. The colony on the far left, Dion Islands, marked in red is believed to have declined and ceased to exist following recent climate change (temperature rise and sea-ice loss) on the Antarctic Peninsula. This previously occupied site is included to give an indication of the current breeding limits. These parameters give no indication of why the Ruppert Coast colony, found breeding on the ice shelf in only one year, relocated onto this ice shelf in 2012. Mean sea-ice concentration (blue) is recorded as a percentage for March/April when emperors prospect and recruit at breeding sites. The figures are calculated using synthetic aperture radar measurements for all dates in these two months for the years 1998–2007. Latitude (red) is the latitude of the colony location from Fretwell et al. 2012 and Wieneke 2012, with the addition of the newly found Larsen Ice Shelf colony described in this paper. Mean temperature is based on a yearly mean for 2000–2004 based on the RACMO climate model.