1 00:00:00,160 --> 00:00:04,160 2 00:00:04,160 --> 00:00:08,330 On March 17, the Arctic region reached a milestone 3 00:00:08,330 --> 00:00:12,330 …the second-lowest sea ice maximum extent since satellite measurements began. 4 00:00:12,330 --> 00:00:16,780 The four lowest maximum Arctic extents on record have been in the last four years, 5 00:00:16,780 --> 00:00:21,130 according to analysis from NASA and the National Snow and Ice Data Center. 6 00:00:21,130 --> 00:00:25,130 This year’s maximum extent reached 5.59 million square miles. 7 00:00:25,130 --> 00:00:29,130 But…what does that really mean? 8 00:00:29,130 --> 00:00:33,140 How, and why, do we track sea ice? 9 00:00:33,140 --> 00:00:37,140 We’ve got a good record of extents since the late 1970s. 10 00:00:37,140 --> 00:00:41,640 So by now, the record of the Arctic ice is clearly 11 00:00:41,640 --> 00:00:45,640 one of a decreasing ice cover. 12 00:00:45,640 --> 00:00:50,420 To answer some of my questions, I talked with Dr. Claire Parkinson, 13 00:00:50,420 --> 00:00:54,600 who has been studying sea ice from space for the past four decades. 14 00:00:54,600 --> 00:00:58,730 I got a job at NASA’s Goddard Space Flight Center in July of 1978, 15 00:00:58,730 --> 00:01:02,920 and I’ve been here ever since 16 00:01:02,920 --> 00:01:07,220 and I’ve had the phenomenal opportunity of getting to start 17 00:01:07,220 --> 00:01:12,370 when the satellite data were still fairly new and when, 18 00:01:12,370 --> 00:01:16,370 at Goddard, people were trying to figure out 19 00:01:16,370 --> 00:01:20,550 how to use the satellite data to reveal information about the Earth. 20 00:01:20,550 --> 00:01:24,550 After several years when we started getting a longer record, 21 00:01:24,550 --> 00:01:29,370 then our attention got changed into 22 00:01:29,370 --> 00:01:33,430 “Well what kinds of trends are we seeing in sea ice?” 23 00:01:33,430 --> 00:01:37,730 We’ve maintained this record of sea ice and we recognize now 24 00:01:37,730 --> 00:01:41,730 that it’s very important for climate change, 25 00:01:41,730 --> 00:01:45,890 because sea ice is one of the variables in the Earth system that has been changing 26 00:01:45,890 --> 00:01:49,980 the most dramatically, especially in the Arctic. 27 00:01:49,980 --> 00:01:54,140 But sea ice doesn’t just react to warming global temperatures… 28 00:01:54,140 --> 00:01:59,320 it can actually accelerate the temperature increases. 29 00:01:59,320 --> 00:02:03,450 Now the less sea ice coverage feeds back 30 00:02:03,450 --> 00:02:08,080 into the warming, because if you’ve got less sea ice cover, 31 00:02:08,080 --> 00:02:12,270 that means less of the sun’s radiation that comes down 32 00:02:12,270 --> 00:02:16,280 to the surface will get reflected back. 33 00:02:16,280 --> 00:02:20,490 Sea ice fluctuates with the seasons, growing during the cold, 34 00:02:20,490 --> 00:02:25,930 dark winters until reaching an annual maximum extent 35 00:02:25,930 --> 00:02:30,980 in February or March in the Arctic, and then shrinking through the summer 36 00:02:30,980 --> 00:02:35,030 until reaching a minimum in September. 37 00:02:35,030 --> 00:02:39,040 In the Arctic case, in late summer, it extends over about 5 million square kilometers. 38 00:02:39,040 --> 00:02:43,050 In late winter, it extends way further, over about 39 00:02:43,050 --> 00:02:47,060 15 million square kilometers, which is about one and a half times the area of Canada. 40 00:02:47,060 --> 00:02:51,240 So studying sea ice 41 00:02:51,240 --> 00:02:55,250 includes tracking how it changes seasonally. Rather than just looking 42 00:02:55,250 --> 00:02:59,260 at the annual summer minimum, scientists track how the ice changes throughout the year, 43 00:02:59,260 --> 00:03:03,270 to get a fuller picture of change. 44 00:03:03,270 --> 00:03:07,280 Every month of the year has decreases in the Arctic and it doesn’t mean 45 00:03:07,280 --> 00:03:11,340 every single year has less ice than the year before, 46 00:03:11,340 --> 00:03:22,085 but it means that, overall, the trend is downward.