In Alaska's Chukchi Sea: Shell Resumes Offshore Drilling as Nearby Walruses are Forced Onshore
by Nick Sundt, World Wildlife Fund, September 26, 2012
The story of this year's Arctic sea ice decline did not end on 16 September when the sea ice reached its official minimum extent for the Arctic overall (see "An Unprecedented Planetary Distress Signal": Arctic Sea Ice Extent Bottoms Out at a Record Low, WWF Climate Blog, 19 September 2012). The decline has continued in the Chukchi Sea -- with momentous consequences. While the National Ice Center indicated that a large "marginal ice zone" was present north of Alaska on 16 September, that zone continued to decline and on 24 September the marginal ice zone had been entirely replaced by open water. The lack of sea ice allowed Royal Dutch Shell Alaska to resume drilling in the Chukchi on 24 September, after ice forced the company to suspend drilling on 10 September. In contrast, the lack of sea ice also has compelled a growing number of walruses nearby at Hanna Shoal to abandon that preferred feeding area and to swim towards land where they are hauling-out. As in 2007, 2009, 2010 and 2011, it now appears likely that we again will see large numbers of walruses huddled along Alaska's beaches, in iconic images that will starkly illustrate the massive disruption that is occurring in the Arctic as the region rapidly warms.
Above (click to enlarge): Hanna Shoal (near top middle of map), a highly productive shallow area favored by walruses, is about 80 nautical miles from the closest land and about 140 nautical miles from Point Lay. The hatched areas to the south and southwest of Hanna Shoal are oil leases. Among them is the "Burger prospect" around 25 miles to the southwest of the shoal, where Shell is presently drilling. Source: University of Texas Center for Research in Water Resources.
Just a month ago, large numbers of walruses were being sighted in the Hanna Shoal area. Most of the walruses were females and their offspring (most of the males haul out elsewhere in Alaska). Observers of the Chukchi Offshore Monitoring in Drilling Area (COMIDA) marine mammal aerial survey project reported seeing nearly 1,800 walruses on 21 August. The U.S. Coast Guard icebreaker Healy also was sailing through the area on a scientific mission around that time. The crew and scientists on some days sighted hundreds of walruses hauled out on the sea ice or swimming in the water. Among the walruses in the area were 40 that had been tagged with radio transmitters earlier this year, and monitored on a daily basis by the U.S. Geological Survey (see the USGS Walrus radio-tracking in the Chukchi Sea 2012 page).
Above (click for larger version): Walruses -- nearly half of which are smaller young walruses -- hauled out on remaining sea ice in the Hanna Shoal area on 19 August 2012. The photo was taken by BMCM Timothy Sullivan, U.S. Coast Guard. He was aboard the USCGC Healy which was on a research cruise in the Chukchi Sea, including Hanna Shoal. Source: BMCM Timothy Sullivan, U.S. Coast Guard.
Overall Arctic sea ice extent continued to decline until 16 September, when the National Snow and Ice Data Center indicated that it had reached its minimum extent for the year (see "An Unprecedented Planetary Distress Signal": Arctic Sea Ice Extent Bottoms Out at a Record Low, WWF Climate Blog 19 Sep 2012). As the figure below indicates, there was at that time a "marginal ice zone" (shown in yellow) in the area of Hanna Shoal off the Alaska coast. The walruses on the Alaska side of the Chukchi were concentrated on that remaining ice, including all the walruses tagged and monitored by the USGS.
Above (click on map for larger version): Sea ice conditions in the Chukchi sea on 16 September 2012, the day of the 2012 Arctic sea ice minimum. At the time a marginal sea ice zone remained off the coast of Alaska over Hanna Shoal. Yellow indicates marginal sea ice and red indicates areas where 8/10 or more of the surface is sea ice. Source: National Ice Center.
But since 16 September, the marginal ice zone in the Hanna Shoal area has continued to decline and on 24 September the National Ice Center indicated for the first time in 2012 that the marginal ice zone was gone and designated the entire area as open water, as shown in the map below.
Above (click on map for larger version): Sea ice conditions in the Chukchi sea on 24 September 2012. For the first time in 2012, the National Ice Center showed no marginal sea ice zone over Hanna Shoal. National Ice Center. Yellow indicates marginal sea ice and red indicates areas where 8/10 or more of the surface is sea ice. Source: National Ice Center.
On the same day (24 September) that the National Ice Center indicated an absence of marginal sea ice in the Chukchi Sea off of Alaska, Shell's Noble Discoverer drillship [link includes current coordinates] resumed drilling in the Chukchi near Hanna Shoal. But simultaneously, the walruses that had thus far managed to find enough ice over Hanna Shoal were compelled to head for the Alaskan shoreline. Among them were walruses tagged with radio transmitters that are monitored by the USGS. Where the tagged walruses had previously all been tightly concentrated over Hanna Shoal, on 24 September the USGS Walrus Tracking Map indicated that one of the tagged walruses already had left the shoal and was along the Alaska coast. In the days since then, more of the tagged walruses have moved to haulouts on land along Alaska's shoreline, especially near Point Lay. Others still are swimming toward land. See the map below for 27 September at 4 am (0400 hrs), where the purple dots show the locations of tagged walruses and the purple lines show their previous positions. Note that when the tagged walruses are close to each other, only a single dot may be visible.
Above: Map showing the positions on 27 September 2012 (purple dots) and past tracks (purple lines) of the walruses tagged with radio transmitters and monitored by the USGS (40 walruses were originally tagged). Note that when the tagged walruses are close to each other, only a single dot may be visible. A week earlier, when still some marginal sea ice remained, the walruses were concentrated in the purple area roughly between N71.5o and N72.0o.
WWF has received confirmation from observers in Alaska that the walruses indeed are hauling-out on land along the Alaskan coast of the Chukchi. We can expect in coming days and weeks to witness the kind of scene we've seen in recent years marked by dramatically low sea ice extent: thousands or even tens of thousands of walruses packed together in conditions that are difficult and -- particulary for the smaller, younger walruses -- dangerous. The photos below show the haulouts near Point Lay, Alaska, in 2011. Observers estimated that 20,000 walruses hauled out there.
Above and below: During COMIDA flight 235 [PDF] on 19 August 2011, observers reported " Approximately 10,000 walruses were observed hauled out on land slightly north of Point Lay" (click on image for larger high resolution image). Less than a week later, COMIDA observers on 24 August estimated that the number of walruses had doubled to roughly 20,000. Source: Rebecca Shea (National Marine Mammal Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration).
Online Resources:
Postings on the WWF Climate Blog about walruses and the haul-outs in 2009, 2010 and 2011: see link:
No comments:
Post a Comment