Dr. Jeff Masters on Polar Ice Cap Melt, Alaska Storm, etc.

Half of the polar ice cap is missing: Arctic sea ice hits a new record low

Published: 8:53 PM GMT on September 06, 2012

Extraordinary melting of sea ice in the Arctic this summer has shattered the all-time low sea ice extent record set in September 2007, and sea ice continues to decline far below what has ever been observed. The new sea ice record was set on August 26, a full three weeks before the usual end of the melting season, according to the National Snow and Ice Data Center. Every major scientific institution that tracks Arctic sea ice agrees that new records for low ice area, extent, and volume have been set. These organizations include the University of Washington Polar Science Center (a new record for low ice volume), the Nansen Environmental & Remote Sensing Center in Norway, and the University of Illinois Cryosphere Today. A comprehensive collection of sea ice graphs shows the full story. Satellite records of sea ice extent date back to 1979, though a 2011 study by Kinnard et al. shows that the Arctic hasn’t seen a melt like this for at least 1,450 years (see a more detailed article on this over at skepticalscience.com.) The latest September 5, 2012 extent of 3.5 million square kilometers is approximately a 50% reduction in the area of Arctic covered by sea ice, compared to the average from 1979 – 2000. The ice continues to melt, and has not reached the low for this year yet.


Figure 1. A sunny, slushy day at the North Pole on September 1, 2012. Webcam image courtesy of the North Pole Environmental Observatory.


Figure 2. Sea ice extent on September 5, 2012, showed that half of the polar ice cap was missing, compared to the average from 1979 – 2000. Image credit: National Snow and Ice Data Center.

Why the Arctic sea ice is important
Arctic sea ice is an important component of the global climate system. The polar ice caps help to regulate global temperature by reflecting sunlight back into space. White snow and ice at the poles reflects sunlight, but dark ocean absorbs it. Replacing bright sea ice with dark ocean is a recipe for more and faster global warming. The Autumn air temperature over the Arctic has increased by 4 – 6°F in the past decade, and we could already be seeing the impacts of this warming in the mid-latitudes, by an increase in extreme weather events. Another non-trivial impact of the absence of sea ice is increased melting in Greenland. We already saw an unprecedented melting event in Greenland this year, and as warming continues, the likelihood of these events increase.


Figure 3. August set a new record for lowest Arctic sea ice extent. Image credit: National Snow and Ice Data Center.

Figure 4. Arctic sea ice death spiral as plotted by Jim Pettit using data from the Japan Aerospace Exploration Agency.

Huge storm pummels Alaska
A massive low pressure system with a central pressure of 970 mb swept through Alaska on Tuesday, generating hurricane-force wind gusts near Anchorage, Alaska that knocked out power to 55,000 homes. Mighty Alaskan storms like this are common in winter, but rare in summer and early fall. The National Weather Service in Anchorage said in their Wednesday forecast discussion that the forecast wind speeds from this storm were incredibly strong for this time of year–four to six standard anomalies above normal. A four-standard anomaly event occurs once every 43 years, and a five-standard anomaly event is a 1-in-4800 year event. However, a meteorologist I heard from who lives in the Anchorage area characterized the wind damage that actually occurred as a 1-in-10 year event. A few maximum wind gusts recorded on Tuesday during the storm:

McHugh Creek (Turnagain Arm)… … ..88 mph
Paradise Valley (Potter Marsh)… … 75 mph
Upper Hillside (1400 ft)… … … … 70 mph
Anchorage port… … … … … … … .63 mph

The storm has weakened to a central pressure of 988 mb today, and is located just north of Alaska. The storm is predicted to bring strong winds of 25 – 35 mph and large waves to the edge of the record-thin and record-small Arctic ice cap, and may add to the unprecedented decline in Arctic sea ice being observed this summer.


Figure 5. An unusually strong storm formed off the coast of Alaska on August 5 and tracked into the center of the Arctic Ocean, where it slowly dissipated over the next several days. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this natural-color mosaic image on Aug. 6, 2012. The center of the storm at that date was located in the middle of the Arctic Ocean. Image credit: NASA.

Arctic storms may be increasing due to climate change
This week’s Alaskan storm is the second unusually strong low pressure system to affect the Arctic in the past month. On August 4 – 8, a mighty storm with a central pressure of 963 mb raged through the Arctic, bringing strong winds that helped scatter and break up Arctic sea ice. According to a detailed post at NASA Earth Observatory, that storm was in the top 3 percent for strongest storms ever recorded north of 70 degrees latitude. A study of long-term Arctic cyclone trends authored by a team led by John Walsh and Xiangdong Zhang of the University of Alaska Fairbanks found that number and intensity of Arctic cyclones has increased during the second half of the twentieth century, particularly during the summer. Dr. Zhang explained that climate change has caused sea ice to retreat markedly in recent decades and has also warmed Arctic Ocean temperatures. Such changes may be providing more energy and moisture to support cyclone development and persistence. The strong storms of this week and a month ago would have had far less impact on the ice just a decade ago, when the sea ice was much thicker and more extensive.

A sea ice decline double-whammy
The monster Arctic storms like we’ve seen this year have sped up the rate of sea ice loss, but increased water temperatures and air temperatures due to human-caused global warming are the dominant reasons for the record melting of the Arctic sea ice. A July 2012 study by Day et al. found that the most influential of the possible natural influences on sea ice loss was the Atlantic Multi-decadal Oscillation (AMO). The AMO has two phases, negative (cold) and positive (warm), which impact Arctic sea ice. The negative phase tends to create sea surface temperatures in the far north Atlantic that are colder than average. In this study, the AMO only accounted for 5% – 31% of the observed September sea ice decline since 1979. The scientists concluded that given the lack of evidence that natural forces were controlling sea ice fluctuations, the majority of sea ice decline we’ve seen during the 1953 – 2010 period was due to human causes.

from:    http://www.wunderground.com/blog/JeffMasters/article.html

Jeff Masters on Alaska Weather, Sean, etc.

Dr. Jeff Masters’ WunderBlog

Alaska blizzard pushes 8-foot storm surge into Nome; Sean heads towards Bermuda
Posted by: JeffMasters, 2:47 PM GMT on November 10, 2011 +3
The most powerful storm to affect the Bering Sea coast of Alaska since 1974 is slowly winding down today, after pounding Alaska’s west coast and Eastern Siberia with hurricane-force winds, a destructive storm surge more than 8 feet high, waves up to 40 feet high, and heavy snow. The highest wind gust recorded during the storm, 89 mph, was at Wales at the western tip of the Seward Peninsula, which forms the U.S. side of the Bering Strait. Hurricane force gusts were observed at seven locations in Alaska:Cape Lisburne… 81 mph at 7 am Wed
Gambell… … … 74 mph at 6 pm Tue
Kotzebue… … ..74 mph at 6 am Wed
Point Hope… … 78 mph at 5 am Wed
Savoonga… … ..76 mph at 7 pm Tue
Tin City… … ..85 mph at 12 am Wed
Wales… … … ..89 mph at 1:42 am Wed

A storm surge of 8.6 feet hit Nome, Alaska near 9 pm EST last night, pushed inland by sustained winds that reached 45 mph, gusting to 61 mph. Large waves on top of the surge encrusted with sea ice battered the coast, causing extensive damage and coastal flooding. Significant wave heights at the Bering Sea buoy north of the Aleutian Islands reached 40 feet during the peak of the storm. The last time Nome, Alaska saw a storm this strong was November 11 – 12 1974,when the city experienced sustained winds of 46 mph with gusts to 69 mph, a pressure that bottomed out at 969 mb, and a storm surge of 13 feet. The center of yesterday’s storm moved ashore over eastern Siberia near 12 UTC with a central pressure of 945 mb. The storm’s central pressure had risen to 958 mb this morning, with the center of the storm now located north of Siberia over the Arctic.


Figure 1. Observed storm surge at Nome, Alaska (green line). MLLW = Mean Lower Low Water, the water level at the lowest tide of the month. The top storm surge of 8.6 feet occurred near 02 GMT this morning (9 pm EST November 9, 2011.) Image credit: NOAA Tides and Currents.

My related blog posts:
Climate change likely to worsen erosion along the Alaska coast
The future of intense winters storms

Tropical Storm Sean
Tropical Storm Sean is on the move towards the northeast, towards a brush with Bermuda. Infrared satellite loopsreveal that Sean has not changed much in organization this morning. The storm has a respectable amount of heavy thunderstorm activity near its center that is relatively shallow, and Sean has at times been able to close off an eyewall, and has a ragged-looking eye. Bermuda radar shows one strong rain band from Sean has affected the island, with the bulk of Sean’s heavy thunderstorms well to the island’s southwest. Sustained winds at the Bermuda airport have been under 30 mph this morning, and Bermuda picked up 0.08″ of rain yesterday, and 0.24″ as of 9 am EST today. Sustained winds at buoy 41048, about 300 miles west of Bermuda were 40 mph at 7:50 am EST. Strong upper-level winds out of the west are creating about 20 knots of wind shear over Sean, which is low enough to allow some slow development. Ocean temperatures have fallen to 25°C (77°F), which just below the 26°C threshold typically needed for a tropical storm to maintain its strength.


Figure 2. Morning satellite image of Tropical Storm Sean.

Forecast for Sean
The latest SHIPS model forecast predicts wind shear will remain about where it is now through Friday morning. However, ocean temperatures will gradually cool to 24°C during this time, and it is questionable whether Sean will have a favorable enough environment to strengthen into a hurricane. The computer models show little development of Sean, with none of our reliable models predicting it will become a hurricane. Bermuda is the only land area that need concern itself with Sean, as the storm is now caught in a trough of low pressure that will accelerate the storm to the northeast. The center of Sean could pass close enough to Bermuda to bring the island heavy rain squalls and sustained winds of 40 – 45 mph on Friday. NHC is giving a 52% chance that Bermuda will receive tropical storm-force winds of 39 mph. Wind shear will rise to 30 – 50 knots on Friday, which should be able to rip the storm apart by Saturday.

Jeff Masters