NASA Watches from Space as Arctic Sea Ice Reaches Sixth Lowest Minimum Extent

Narration: Katy Mersmann & Melinda Webster

Transcript:

1

00:00:00,120 --> 00:00:04,250

Arctic sea ice reached its annual minimum

2

00:00:04,250 --> 00:00:08,450

extent September 19, and again on September 23, 2018.

3

00:00:08,450 --> 00:00:12,640

NASA works with the National Snow and Ice Data Center to track sea ice in the Arctic.

4

00:00:12,640 --> 00:00:16,840

Each year, it grows to a maximum extent through the winter

5

00:00:16,840 --> 00:00:21,030

and shrinks to its minimum extent at the end of summer.

6

00:00:21,030 --> 00:00:25,350

This year’s minimum sea ice extent reached 1.77 million square miles.

7

00:00:25,350 --> 00:00:29,400

It’s tied with 2008 and 2010 as the sixth lowest

8

00:00:29,400 --> 00:00:33,590

sea ice minimum since consistent satellite records began.

9

00:00:33,590 --> 00:00:37,790

We need every single data point to string together into a really nice time series and that

10

00:00:37,790 --> 00:00:42,000

helps us understand interannual variability and also the long-term trend.

11

00:00:42,000 --> 00:00:46,080

NASA has been observing changes in the polar sea ice covers for over 40 years.

12

00:00:46,080 --> 00:00:50,270

NASA studies the Arctic and Antarctic

13

00:00:50,270 --> 00:00:54,500

sea ice covers in several ways. So NASA’s Operation IceBridge,

14

00:00:54,500 --> 00:00:58,590

it’s an airborne mission – they fly every spring over the sea ice cover to measure the snow and the sea ice

15

00:00:58,590 --> 00:01:02,830

And another way that we measure sea ice is using passive microwave.

16

00:01:02,830 --> 00:01:06,900

So this is an instrument that can see through clouds essentially and tells us where the ice is.

17

00:01:06,900 --> 00:01:10,980

In addition to the 40-year passive microwave record,

18

00:01:10,980 --> 00:01:15,090

a new NASA satellite called ICESat-2 will provide a new

19

00:01:15,090 --> 00:01:19,280

and important collection of sea ice observations.

20

00:01:19,280 --> 00:01:23,460

ICESat-2 just launched and what it’s measuring is really, really exciting.

21

00:01:23,460 --> 00:01:27,680

So I was talking before about passive microwave tells us where the sea ice is.

22

00:01:27,680 --> 00:01:31,890

What ICESat-2 is going to do is to tell us how thick the ice cover is.

23

00:01:31,890 --> 00:01:35,920

It’s measuring the freeboard of the ice cover; this is the amount of the ice that floats

24

00:01:35,920 --> 00:01:40,090

above the sea level line, just like an ice cube in a glass of water, and we can use

25

00:01:40,090 --> 00:01:44,210

that to calculate just how thick the underlying ice is.

26

00:01:44,210 --> 00:01:48,290

Thickness is an important measure of sea ice health, and studying it

27

00:01:48,290 --> 00:01:52,510

helps scientists understand how the Arctic is changing.

28

00:01:52,510 --> 00:01:56,700

We’re seeing a decline in sea ice thickness, in sea ice age, meaning that the ice

29

00:01:56,700 --> 00:02:00,880

is no longer perennial, but it’s transitioning more to seasonal type ice,

30

00:02:00,880 --> 00:02:04,990

and also in its extentThere are two types of ice in the Arctic,

31

00:02:04,990 --> 00:02:09,140

there’s old ice and young ice. Perennial ice being the stuff

32

00:02:09,140 --> 00:02:13,330

that lasts years, and then seasonal ice, the stuff that melts back

33

00:02:13,330 --> 00:02:17,510

every summer. So there are some pretty big differences between those two ice types

34

00:02:17,510 --> 00:02:21,690

Starting with the seasonal ice. This is the ice that forms when the

35

00:02:21,690 --> 00:02:25,760

ocean freezes, so it actually has salt in it, it’s very saline, because it’

36

00:02:25,760 --> 00:02:29,860

forming from sea water. This stuff is usually thinner than the older ice

37

00:02:29,860 --> 00:02:34,050

and because it has more salt, it’s usually weaker in its structure,

38

00:02:34,050 --> 00:02:38,090

so it’s easier to break up. For the older ice, this stuff’s

39

00:02:38,090 --> 00:02:42,280

usually a lot thicker, a lot fresher and stronger, so it has more resilience

40

00:02:42,280 --> 00:02:46,410

during the summer melt season than thinner ice.

41

00:02:46,410 --> 00:02:50,590

With the successful launch of ICESat-2, NASA scientists will link the records of sea ice

42

00:02:50,590 --> 00:02:54,810

extent, age and thickness to better understand

43

00:02:54,810 --> 00:03:05,068

how Earth’s polar regions are changing.