Menu Close

Climate change is flooding the Arctic Ocean with light – what it means for the species that live there

Sea ice with sun on horizon.
The polar night can last for weeks and even months in the high Arctic. Rowan Romeyn/Alamy Stock Photo

This is a transcript of episode 5 of The Conversation Weekly podcast, How climate change if flooding the Arctic Ocean with light. In this episode, two experts explain how melting ice in the far north is bringing more light to the Arctic Ocean and what this means for the species that live there. And we hear from a team of archaeologists on their new research in Tanzania’s Olduvai Gorge that found evidence of just how adaptable early humans were to the changing environment.

NOTE: Transcripts may contain errors. Please check the corresponding audio before quoting in print.

Dan Merino: Hello and welcome back. From The Conversation, I’m Dan Merino in San Francisco.

Gemma Ware: And I’m Gemma Ware in London and you’re listening to The Conversation Weekly, the world explained by experts.

Dan: In this episode, two Arctic Ocean researchers explain how melting ice in the far north leads to more light in the Arctic – and what that means for sea life.

Karen Filbee-Dexter: Our ecosystems are responding, because these changes are really dramatic and they’re noticeable.

Gemma: And we talk to a team of archaeologists about the early humans who lived in Tanzania’s Olduvai Gorge 2 million years ago.

Makarius Peter Itambu: In this scenario, hominims from Oldupa maintained the very same toolkit.

Dan: So Gemma, today we’re going on a journey up to just about as far north as we can go, all the way up to the Arctic. What do you imagine when I say the word Arctic?

Gemma: I feel a bit cold already, and I guess I think of big expanses of snow and ice, drifting, like wind. Maybe the odd polar bear. And I guess in winter it’s just dark.

Dan: That’s a great example if you were to stay on top of the ice, but there’s a whole different world beneath it. And it’s full of ocean, like teeming alive.

Gemma: We know climate change is causing some of this ice to melt though, right?

Dan: Yeah totally… well some of the ice melts every summer. The sun’s up and then in winter when the sun goes away it grows back, but that ice is melting much more than it used to. So in September 2020, Arctic sea ice covered 3.74 million square kilometres.

Gemma: Well that sounds like a lot…

Dan: It does. But it’s the second smallest measurement ever. And only roughly half of what was measured in 1980.

Gemma: So what does that melting sea ice mean for all that teeming sea life living in the Arctic Ocean?

Dan: It’s not clear cut… it’s not all bad news even. Different scientists are studying all sorts of changes to see how it’s going to matter for the life in the Arctic, but one of the things they’re looking at is light. If there’s less and less sea ice, more light gets down into the ocean. And in the dark winter, where ice would normally cover the ice caps, it’s not there, so ships are driving through more and more and bringing with them a lot of artificial light.

I spoke to two researchers who’ve been spending a lot of time in the cold icy waters way up north to study all of this. And let’s just let one of them kind of set the scene. So Gemma, and all you listeners out there, imagine you step off a plane in the far, far north. Here’s what you might see.

Karen: So you have these places that are so covered in snow and ice, that they almost have a moon landscape of just bare rock in the summer. No leaves, no forest, no trees.

Dan: That’s Karen Filbee-Dexter, a research fellow at the university of Western Australia and a scientist at the Institute of Marine Research in Norway. She’s talking about the shoreline there. The long dark winters make it so that even in the sunny summer, the landscape is barren. But in the ocean, there’s a very a different story.

Karen: And then you go under water and you have to go a little bit deeper, but when you dive you sort of past this zone, where all of a sudden these amazing underwater forests appear.

Dan: These forests are not made of trees of course, but of kelp, attached to the sea floor, swaying in the currents.

Karen: So you have these long blades that will float in the water column and then they, just like a forest, shade light and create these understory conditions that fish and animals use and live in the same way as a forest does on land.

Dan: And how big are we talking? And I’m thinking Redwood trees, or am I thinking a bush in my yard kind of size?

Karen: It depends on the species and it depends on the forest. So, the first kelp forest that I dove on in the Arctic was about one to two meters tall. And it was actually in Arctic Norway. But the largest kelp forest that I’ve been in the Arctic has been in Canada. So there is an area in Nunavut where the kelp was about three to five meters tall. And that was spectacular.

Read more: Arctic Ocean: climate change is flooding the remote north with light – and new species

Dan: Until recently, not too much was known about Arctic kelp. What kind grow where, or even how much there is.

Karen and her colleagues at the Arctic Kelp project, an aptly named group of universities, institutions and NGOs across Canada, are trying to catalogue which kelps are growing in the Arctic today, and how the warming temperatures are going to affect where they grow in the future.

Karen has spent a lot of time underwater using scuba gear to study these kelp ecosystems. But for many of these places, you can only access them in the short window when sea ice disappears.

Karen: So that’s what’s incredible about these habitats. They’re covered by ice. For sometimes more than half of the year and they require light to live. So they’re just growing based on light that reaches the sea floor in this very short period when the ice is not there.

A scuba diver swims through kelp fronds.
A diver explores a four-metre-high sugar kelp forest off Southampton Island, Canada. Ignacio Garrido/ArcticKelp, Author provided

Dan: Kelps, and well, everything in the Arctic Ocean, spend a huge amount of time in the dark, either because it’s winter the sun hasn’t come up for months, or because the sea surface is covered by ice. When the ice melts and daylight returns, kelps grow really fast. They have to, it’s a short growing season. But that growing season is getting longer.

Karen: What’s happening now in the Arctic is we have this massive and dramatic loss of sea ice. So this means that a large amount of Arctic coastline, which is normally covered in ice and normally doesn’t get that much light is now suddenly sort of open to, to the sun.

Dan: All you gardeners out there will know this equation: more sunlight, more growth. As Arctic temperatures warm due to climate change and sea shrinks, these underwater forests are expanding, and kelp is now growing in places where it didn’t used to.

Karen: So based on, how the conditions have changed from 1950 to now, we can predict that the migration rate in the Arctic is about, 20km per decade. So this sort of poleward expansion is definitely marching along, and there’s all the evidence that these changes are accelerating.

Daniel: 20km per decade is pretty fast for a bunch of trees

Karen: Yes, the marching forest. It is definitely something out of a Lord of the Rings movie. But the rules are different in the Arctic, right? So, so it’s changing much faster than the rest of the world. Everything happening there is happening at, you know, two to three times the rate of change. So, we’re already way into the climate change future, along our Arctic coastlines. So it’s not surprising that our ecosystems are responding because these changes are really dramatic and they’re noticeable. And they’re going to put a lot of pressure on marine species to move.

Dan: These changes which are causing kelp to expand and move are not good everywhere though. A lot of the Arctic coastline is made of permafrost.

Karen: This is essentially frozen soil. When that frozen soil thaws all of that dirt and sediment just flushes into the coastal zone and creates a lot of turbidity.

Dan: This murky brown water prevents light from reaching the seafloor and the kelps growing there.

Another side effect of climate change is that glaciers and ice sheets are melting and dumping huge amounts of fresh water into coastal areas, that can also harm kelp.

So while not every change is good for kelps and seaweeds way up north, overall Karen says that predictive models show the future is looking pretty good for Arctic kelp forests.

In many other parts of the world, these ecosystems are shrinking, so it’s kind of cool that, as least to some extent, these losses are being offset up north. And a large expansion of underwater kelps might actually help slow climate change ever so slightly.

Just like trees on land, kelps rely on carbon dioxide to grow. Expanding kelp forests in the Arctic could become a pretty significant carbon sink. When these kelps die, they just drift slowly to the deep dark depths of the ocean, and because it’s so cold, they don’t really rot either. Instead, they just sit there, keeping corbon dioxide locked up at the bottom of the ocean.

There are other more tangible benefits to larger kelp forests too. It’s great habitat for marine life.

Karen: They’re going to have a higher canopy height and a higher biomass. This means that there’s more space for animals to live in. So basically more rooms in the house, more structure, more niches for different species to occupy.

It also probably will mean a shift in species. So most seaweeds and most kelps in the Arctic were almost kicked out in the last ice age and then they’ve been slowly inching their way back in. And some of them have done a better job and have adapted to these really extreme conditions, better than others.

Dan: Kelps aren’t the only thing that likes less sea ice. Us humans do as well. As sea ice decreases in both summer and winter, the formerly dark polar night that last for weeks or months, is now being lit up like never before by boats and the artificial light they bring in with them. This is a big deal to the multitudes of sea creatures that have adapted over millions of years to the darkness of the polar winter. One group of scientists is studying how this new influx of light is changing the behaviour of these animals.

Jørgen Berge: My name is Jørgen Berge, I’m a professor in marine biology at UIT, the Arctic University of Norway.

Dan: Jørgen, unlike most people, doesn’t actually mind the long dark, polar, winter. I spoke to him late last year, when the polar night in Norway had just begun

Jørgen: We actually just started the polar night items sitting now in Tromsø at 70 degrees north. The sun orbits around our horizon for 24 hours a day for two months in a row. There is still clear difference between day and night. But that difference becomes less and less the further north you get. And then once you get up to around 80 degrees, then the human eye is hardly able to distinguish any difference between night and day during the darkest part of the polar night.

But the polar night is certainly not just dark. It’s actually all about different kinds of light. Both background illumination from the sun, the aurora borealis the moon, also biological light.

Dan: Up until fairly recently, scientists used to think that the darkness of the polar night was uninteresting, devoid of life. But a research project that Jørgen started back in 2006 changed all that – and kind of by accident. His team was actually looking at how retreating sea ice would affect the marine ecosystem in an Arctic Fjord.

Jørgen: So we had to be there in the late autumn to deploy instruments that would then be in place and do measurements when the sun came back. But then as more or less a byproduct, the instruments were also doing measurements during the dark polar night. But when we got these data back, we started to realise that, hang on something, something is actually happening here.

Dan: What him and his team found changed scientists’ understanding of the polar night. The polar night isn’t not boring, far from it in fact.

Jørgen: So it’s a system that is in fact in full operation. Seabirds, fishes, zooplankton. It’s just so fascinatingly full of life during the, during the dark polar night.

Dan: One of the processes Jørgen and his colleagues has studied is called diel vertical migration.

Jørgen: That is the behaviour where organisms – zooplankton and fish – they move up from the deep up into the shallow, during nighttime and go migrate down into the deep, during daytime.

Dan: This is entirely controlled by light, so researchers just assumed it would stop. The polar night is just perpetual darkness after all.

Jørgen: It turns out that it doesn’t stop, it’s ongoing. One of the things that we have started to realise is how extremely intimately, these organisms are connected to the light climate, to ambient light.

Dan: Even with the sun gone during the winter months, light plays a huge role in the Arctic. The sun still brightens the sky ever so slightly as the earth rotates. Moon cycles also change light levels, and so does the aurora borealis. And creatures react to all of this. But when Jørgen and his colleagues were studying these creatures, they got conflicting data between the instruments they left alone over one winter and the data they collected from their boats. The reason was light pollution from the researchers themselves.

Jørgen: The first year we really didn’t fully really understand why the samples we took never matched the data that we got from acoustic instruments that had been deployed autonomously. But it turns out that these organisms, they are able to respond to extreme small levels of light.

Dan: Jørgen and his team need, well, light to work on their boat, so they use headlamps and floodlights and stuff. For ultra light-sensitive sea creatures, these lights are huge signals. Some swim towards them, some swim violently away. And not just animals near the surface. The team found this happening down to depths of 200 metres below the sea level.

The effect of light pollution could be happening on a large scale, thanks to melting sea ice and increased human presence.

Jørgen: As sea ice retreats, as we start fishing further north, oil and gas exploration, shipping, not the least, more and more human presence in the high Arctic during the polar night, then we also bring with us artificial lights. At the moment we are not able to, to, to say to which degree this really is a problem, but, that is one of the things that we are now really starting to look into.

A large ship covered in yellow lights illuminates the icy water.
Creatures which have adapted to the polar night over millions of years are now suddenly exposed to artificial light. Michael O. Snyder, Author provided

Dan: And melting sea ice, well that’s climate change.

Jørgen: So artificial light, it’s not of course a direct effect of climate change, but it’s certainly related to climate change because as it gets warmer, as there is less sea ice then we see more human presence and human presence will, it means there’s more artificial lights involved.

Dan: So what does this all mean for the fish, zooplankton and other sea creatures that are super-sensitive to light and live in this high Arctic environment? Jørgen says that’s a difficult question to answer.

Jørgen: Personally, I think that we have to look at the effects in two ways. One is the direct effect of light pollution. It does affect organisms there and then. Most likely that effect is limited, because it only last while there is artificial light there. And there’s certainly a limit to the, the geographical extent of that impact.

However, I think there’s another effect that is much more important. And that is how it’s affecting our knowledge about the polar night. To take one example, there’s more and more fisheries the high Arctic during the polar night. If you want to do surveys to give an estimate about how much there is of say haddock or cod, you have to do acoustic surveys with research vessels in the polar night, in where we are fishing. And these measurements might be strongly biased and impaired.

Dan: Essentially what Jørgen is saying is that every measure of arctic fisheries even taken in winter could be way off. By bringing in light, the fishermen and researchers change how fish and other animals behave. This is one of the oldest problems in biology: how to study ecosystems without disturbing them. And I asked him he feels as a scientist, to discover that his own presence could be distorting the results of his research.

Jørgen: Yeah, it sorta makes you feel unwanted. You know, that your presence is affecting the organisms, but it also, as a scientist, it also makes me, maybe wonder and questions. And I find it fascinating trying to understand things I cannot see.

It’s difficult to explain, but to me, when you really go, go up into the high Arctic and you allow yourself to be in the darkness and you start to take in all the senses, the sounds, the light, it’s just a, just a miracle sometimes.

I can still remember one on the experience we had. This was one of the first years when we were up on Svalbard in, early January, and I was out in a small boat out in the middle of the fjord and we turned off the engines. We turned off all lights because we wanted to look for seabirds. And we looked down and we saw this upside down sky filled with blue-green light, and that was just an amazing experience to see all this organisms from big jellies to small unicellular organisms blinking and glowing and moving in all directions. That was a beautiful sight.

Dan: What Jørgen saw was bio-luminescence – light produced by creatures in the Arctic night to communicate with each other. When you live in total darkness, light is, almost paradoxically, one of the most important and useful things there could possibly be. Even to the scientists who study it, the darkness of the polar night is so much more complex than anyone even imagined.

Gemma: I love the idea of the ocean blinking back at you, that’s just so beautiful as Jørgen said.

Dan: It made me want to take a vacation to the polar night in the middle of winter, which I’d never thought I’d say before. But, it is also dangerous, both Karen and Jørgen were talking about polar bears and how you actually have to carry guns, so it’s not all blinky lights and gorgeousness.

Dan: Both Karen and Jørgen have written for The Conversation as part of a series we’re running called Oceans 21. It examines the history and future of the world’s oceans. On The Conversation’s website, we’ve actually got a profile of every ocean on earth and Jørgen and Karen contributed to the one on the Arctic.

Gemma: Yes and our environment editors are publishing really important new research on a regular basis about the ocean. They just published another story about a team of scientists tracking where plastic pollution goes when it enters the water.

This research is part of Oceans 21
Our series on the global ocean opened with five in-depth profiles. Look out for new articles on the state of our oceans in the lead up to the UN’s next climate conference, COP26. The series is brought to you by The Conversation’s international network.

Dan: We’ve put a link to that, and the Oceans 21 series, in the show notes.

Gemma: Coming up, a group of archaeologists talk to us about some of their recent finds from Tanzania. But first, we’ve got a message with some recommended reading from Laura Hood, politics editor and assistant editor at The Conversation in London.

Laura Hood: Hello. My name is Laura Hood. I’m a politics editor for The Conversation here in London. I’ve got two recommendations this week. I worked with a team of psychologists led by Daniel Jolley from the University of Northumbria here in the UK. He told me about some work his team has been doing investigating how young people are being affected by conspiracy theories in the pandemic. Before they got in touch. I hadn’t realised that almost everything we know about conspiracy theories is based on work investigating adults. We know next to nothing about how children encounter and absorb misinformation. So they’ve been conducting surveys with British adolescents to try to work out at what age we’re most vulnerable to conspiracy theories and the extent to which young people are being exposed to them during lockdown. It’s really interesting reading, I think, particularly for parents.

I’d also like to recommend an article written by Mark Toshner, he’s an expert in respiratory medicine at the University of Cambridge. He’s put together a guide for anyone who’s feeling a bit overwhelmed by the scientific information that’s flying around about vaccines right now. He says, he feels really sorry for us trying to absorb all this information and he wants to make it a bit easier. So he’s tackling topics such as what it means when we hear that one vaccine is 90% effective, say, or another one is only 70% effective. Is that something we should be worrying about? Should we be trying to pick and choose our vaccines? He’s also talking about what it means for a vaccine to be potentially less effective against particular types of variant of COVID-19. So it’s useful information at this stage of the pandemic.

Daniel: That was Laura Hood from The Conversation in London.

Gemma: So for our next story, we’re heading to a warmer climate, thankfully, to Tanzania in East Africa and a place called the Olduvai Gorge. It’s known as the birthplace of humanity.

Dan: Birthplace, so how long we talking here?

Gemma: Ages, so about 2 million years or so. And today, archeologists from around the world, come to Olduvai to study the remains of different species of early humans. But scientists are also interested in the ancient environment and what the gorge actually looked like back then.

Dan: So is there a name for studying ancient climates?

Gemma: Yes, and it’s a great one. It’s paleoecology. So basically this is looking for evidence of ancient plants and pollen, and even bits of airborne charcoal by delicately sifting through layers of sediment. So we’ve been talking to a group of researchers who’ve been doing this work in a specific parts of the Olduvai Gorge called Ewass Oldupa, which actually means “the way to the gorge” in the Maa language of the local Masaai and what they’ve found has provided new insights into just how adaptable early humans were to the changing environment around them.

Read more: Finds in Tanzania's Olduvai Gorge reveal how ancient humans adapted to change

Julio Mercader: I’m Julio Mercader and I’m a professor with the University of Calgary, which is in Western Canada.

Gemma: OK, and we’re talking to you today, Julio, about your most recent research that’s just been published. It’s about an area in Tanzania, in East Africa. Can you just give me a bit of context? Why is this part of the world so important for our history?

Julio: Olduvai Gorge is in East Africa, and if you think of it as a region – there is this reef that is splitting the crust of the earth that is allowing volcanoes to spit out lava and ash. But at the same time as the splitting, it’s making the terrain sink. And when that happens, you have water building up that forms lakes and rivers and swamps. And because of that biodiversity tends to be really, really high because nature is a really productive in these kind of a rfit context.

Now in East Africa, which is where Olduvai is, the rift has been alive, so to speak, for more than 20 million years so that when humanity is forming, several million years ago, early humans, like any other animal, are being attracted to the resources that you find in the rift.

Now life near volcanoes was preserved because the eruptions and the sediments covered that up and then archaeologists exposed it. So now imagine an African Pompeii. But this time is much older. It is two million years. And instead of Romans, you want to imagine humans. But these humans are not like you and I, huh? They are early humans, several species. Unlike today when there is only one species. And among them on Olduvai Gorge, you have the first member of our genus, that we say in biology, and that is the genus homo. Right? And so to sum it up, Olduvai Gorge is important because many aspects of early human life have been buried, covered and preserved for posterity. And it’s not only the human fossils, but what we humans did on a daily basis, our activities.

And as you know, the gorge is like a canyon, it’s like a small version of the Grand Canyon. And because there is like a scar in the terrain, you can see the fossils in the remains, popping out from the walls that create the canyon.

Archaeologists working next to a tent on a hillside.
The research site at the Olduvai Gorge. Author provided (no reuse)

Gemma: So it seems like an incredibly important place for archaeologists like you and your colleagues. How long ago are we talking and is this a period of time when different species are actually competing for dominance?

Julio: Well, there is a lot we don’t know about this, but what we do know is that it was 2 million years ago. And at this point, what you have is humans belonging with a several genera. So for example, various homo habilis, and that species belongs with the same genus as you and I. But there is also paranthropus boisei, and other members of the australopithecines.

Now, are they competing directly with one another? From an ecological point of view, maybe not. Maybe not because we know that the adaptations, the morphology of the body, the cranial architecture, the diets may be a little different. So to explain this, imagine different species taking on different niches within the environment.

Gemma: OK, so let’s get into a bit more detail now about the research that you and your colleagues have recently published a paper on. What did you find?

Julio: We uncovered evidence that hominins were coming to a specific location within the gorge, which is on the western side of it. And, they kept coming back.

Gemma: To understand more about what the team of archaeologists found in the gorge, I spoke to two of the Tanzanians who’d worked on the study. Pastory Bushozi and Makarius Peter Itambu. I got them on a slightly dodgy line. So bear with us.

Pastory Bushozi: My name is Pastory Bushozi. I’m a senior lecturer at the University of Dar es Salaam, and archaeologist working on paleoanthropology.

Makarius: My name is Makarius, I’m a lecturer in archaeology, teaching human evolution, paleoenvironment and African stone age.

Gemma: What did you find? What did the ecology of the Olduvai gorge look like when these populations you were studying were living there 2 million years ago?

Makarius: The discovery revealed that the oldest Olduvai hominins used diverse but rapidly changing environments, that range from fern meadows, to woodland mosaics, but also natural band landscape to the lakeside. But also there’s woodland and palm groves, as well as steppes. Those were the kind of environment that looked like during 2 million years ago.

Gemma: So the landscape was changing, you were having forest, you having like a big steppe, you were having grasslands.

Makarius: Right, but the more interesting things, hominims continued to utilise the same toolkit, which is Olduwan. And this is so interesting because we believed that climatic change always trigger technological change, but in this scenario, hominins from Oldupa, it was the Oldupa site, maintain the very same toolkit, the Olduwan stone tools.

Gemma: You were seeing that they were using the same tools throughout that period?

Makarius: Yeah, that was so fascinating that despite of these rapid changes, adaptation to this major geomorphic and ecological transformation did not have any impact.

Gemma: Here’s Julio Mercader again.

Julio: What is interesting here is that over the course of 300,000 years, these Olduwan hominins are coming back to exploit different environments. And so what we have here for the first time is evidence in one place of the diversity of the adaptive tools and strategies that humanity is using to exploit many different ecologies and environments, showing an early example of great adaptability

Gemma: So you were seeing a real ability to use the environment to their benefit?

Julio: That is right. And so to me, this is a real landmark because there is technological dependence, but also the ability to adapt to whatever changes there are happening. And so, in a way it is like the very beginnings of the invasive behaviour typifies any other pioneer.

Gemma: Dr. Bushozi, can I bring you in there. I understand it was you who made one of the oldest discoveries?

Pastory: Yes, it was me, because actually I found those stone tools that were coming on the lower sequence. So I was excited, myself, and I called my colleague to come and see that. That day, everybody was excited. So by then we were collecting everything to see what we were going to do in the lab.

Gemma: And are you able to do research at the moment or is the pandemic stopping your research in the gorge?

Pastory: Because of the pandemic, we are not doing research, but still we are working on the lab. The work I’m doing now is to clean those stone tools by using chemicals so that I can get a good picture on those stone tools, and then after that we are also trying to do get what kind of raw materials, what kind of implement they were using to shape those tools. And then when we go back into the field, we’ll be able to find, trace now where those rocks were coming from.

Gemma: Thank you so much for your time, I really appreciate it.

Makarius and Pastory: Thank you so much.

Gemma: You can read more about the research in a piece that Julio Mercader wrote for The Conversation about their findings.

Alright, that’s it for this week. Thanks to all the academics who’ve spoken to us for this episode - and to The Conversation editors Natasha Joseph, Jack Marley, Hannah Hoag and Laura Hood.

Dan: You can find links to all the expert analysis we’ve mentioned in the episode – and tonnes of other recommended reading – in the show notes. And if you learnt loads and want to read more, click the link to sign up for our free daily email.

Gemma: This episode is co-produced by Mend Mariwany and me, with sound design by Eloise Stevens.

Dan: Our theme music is by Neeta Sarl. Final thanks also to Alice Mason, Stephen Khan and Imriel Morgan.

Gemma: Thanks for listening everybody. Until next time.

Want to write?

Write an article and join a growing community of more than 184,100 academics and researchers from 4,967 institutions.

Register now