Rising Seas: Out-of-Balance Ice Sheets

Narration: LK Ward

Transcript:

1

00:00:00,000 --> 00:00:04,480

Greenland and Antarctica are home to most of the world's glacial ice

2

00:00:04,480 --> 00:00:08,680

that accumulates on land– including its only two ice sheets.

3

00:00:08,680 --> 00:00:11,600

That’s why scientists focus their energy here first

4

00:00:11,600 --> 00:00:14,940

when looking for answers about sea level rise.

5

00:00:14,940 --> 00:00:16,850

Here’s a concerning reality:

6

00:00:16,850 --> 00:00:19,990

Combined, the two regions contain enough ice,

7

00:00:19,990 --> 00:00:22,320

that if it were to melt all at once,

8

00:00:22,320 --> 00:00:26,430

sea levels would increase by nearly 215 feet.

9

00:00:26,430 --> 00:00:29,710

10

00:00:29,710 --> 00:00:32,560

Rising Waters: Out-of-Balance Ice Sheets

11

00:00:32,560 --> 00:00:34,940

Now, that isn’t going to happen anytime soon,

12

00:00:34,940 --> 00:00:39,040

but even a few feet of sea level rise (much less 215)

13

00:00:39,040 --> 00:00:42,630

would be disastrous for the planet’s coastal communities.

14

00:00:42,630 --> 00:00:47,320

For most people, these processes are happening so far away

15

00:00:47,320 --> 00:00:51,070

that’s hard to imagine how melting at the poles even occurs.

16

00:00:51,070 --> 00:00:52,750

Let’s lay some groundwork:

17

00:00:52,750 --> 00:00:58,770

A healthy glacier is one that accumulates the same amount of snowfall and it loses.

18

00:00:58,770 --> 00:01:01,100

It’s a system in balance.

19

00:01:01,100 --> 00:01:05,920

Unfortunately, today’s glaciers and ice sheets are not in balance.

20

00:01:05,920 --> 00:01:08,050

Here’s what that actually looks like:

21

00:01:08,050 --> 00:01:12,100

In Greenland, when warm summer air melts the surface of a glacier,

22

00:01:12,100 --> 00:01:15,270

the meltwater drills holes down through the ice.

23

00:01:15,270 --> 00:01:18,080

It makes its way down to the bottom of the glacier

24

00:01:18,080 --> 00:01:20,800

where it runs between the ice and the bedrock,

25

00:01:20,800 --> 00:01:24,290

and eventually shoots out in a plume at the base of the glacier.

26

00:01:24,290 --> 00:01:28,250

The meltwater plume is lighter because it doesn't contain salt

27

00:01:28,250 --> 00:01:30,060

– it’s freshwater.

28

00:01:30,060 --> 00:01:31,890

It rises toward the surface,

29

00:01:31,890 --> 00:01:35,440

mixing warm, salty ocean water upward in the process.

30

00:01:35,440 --> 00:01:38,930

The warm water then rubs up against the bottom of the glacier,

31

00:01:38,930 --> 00:01:41,530

causing even more of the glacier to melt.

32

00:01:41,530 --> 00:01:43,710

This often leads to calving,

33

00:01:43,710 --> 00:01:47,760

where ice cracks and breaks off into large icebergs.

34

00:01:47,760 --> 00:01:49,470

35

00:01:49,470 --> 00:01:53,510

In addition to melting caused by warm air and a warm ocean,

36

00:01:53,510 --> 00:01:57,920

Antarctica faces another challenge: the bedrock itself.

37

00:01:57,920 --> 00:02:03,530

Researches often split Antarctica into two regions: east and west.

38

00:02:03,530 --> 00:02:07,920

Unlike East Antarctica, the bedrock that makes up West Antarctica

39

00:02:07,920 --> 00:02:11,900

is below sea level, which means it’s actually underwater.

40

00:02:11,900 --> 00:02:16,080

Warmer water has an easier time seeping in between the continental shelf

41

00:02:16,080 --> 00:02:18,940

and the ice sheet, melting the ice from below.

42

00:02:18,940 --> 00:02:23,950

This causes the ice shelves to thin and break off into the ocean.

43

00:02:23,950 --> 00:02:25,540

44

00:02:25,540 --> 00:02:30,610

Melting and ice loss have accelerated at both poles in recent years.

45

00:02:30,610 --> 00:02:33,350

The more we learn about this complicated process,

46

00:02:33,350 --> 00:02:38,600

the more accurately we'll be able to predict sea level rise far into the future.

47

00:02:38,600 --> 00:02:51,520