 It's one o'clock on Tuesday, March the 8th. So you must be watching Science at Soast. I'm your host, Pete McGinnis-Mark. And every week we bring graduate students or postdocs to the studio, which is streaming live from beautiful downtown Honolulu to describe some of their exciting research. Soast, by the way, is the School of Ocean, Earth Science and Technology. And today our guest is Noah Pahoa, who is a graduate student within the Earth Sciences Department. So Noah, welcome. It's a pleasure to have you on the show. I know you're a bit nervous, but this is all meant to be fun. So welcome again. And maybe for the viewers, you can just tell us a little bit about your background. Thank you. Thank you for the invite. Good afternoon, everyone. My name is Noah Pahoa Kanegisa. I am an international graduate student, starting sea level rise here at Soast with Chip Fletcher. I come from the island of Rapa Nui, so another Polynesian island. And I am happy to be here at UH, starting something that affects us all, Polynesian islands. And first of all, Noah, I understand you've just completed your master's degree. So congratulations on that. But you're from Rapa Nui. What brings you from that beautiful island to Honolulu, which is not bad, but must be quite different, isn't it? Yeah, it is different. However, I got my bachelor's degree in Oregon, surprisingly, University of Oregon. And I knew that I wanted to continue my studies. So I was looking for opportunities on where to do that. And when the opportunity of coming to Hawaii arose, I knew that it was the right choice to make, because I wanted to, as I said, continue studying, but I wanted to do it somewhere that it was more relatable. I like Oregon, you know, Hawaii is a little bit more similar to Rapa Nui, in the sense that it's an island, and the Aloha spirit, and even the Hawaiian language. And the Polynesian heritage here must be fairly similar to what you had at home. Totally. Because you come from an island and you're studying on another island, our topic today is sea level rise on Oahu. But I presume that's partly related to climate change and phenomena which will affect not only Hawaii, but also Rapa Nui and elsewhere around the planet. Totally, totally. Climate change, sea level rise is an issue that will affect the whole world in different amounts, but it's going to affect us all. And yeah, especially Pacific islands, lowland Pacific islands. Markets, for example, or... Marquesas, Kiribash. Well, I suspect that the viewers have got some idea on the causes or the rate of advance of climate change. But if we go the first slide, I think you put together a couple of graphs just to get us a little concerned. Can you explain to us what we're seeing? No, I think it's the National Oceanographic and Atmospheric Administration. Right, you're showing two-time horizons, right? Yeah, correct. So in this slide, we're looking at two different projections of what the global sea level is going to be up to the year 2100 in the case of the top graph and up to the year 2150 for the bottom graph. The top graph is from, as you said, from the National Oceanic and Atmospheric Administration. From a paper written by Street et al. in 2017. And the bottom graph came out in a report by the Intergovernmental Panel on Climate Change very recently. And these are the values that we would expect to see in the coming years associated to the global rise of sea level. Perhaps the viewers can't see in detail the numbers. Just the order of magnitude, like by 2050 or the turn of the century, these models predict how much sea level rise. These models predict anywhere from like one meter, which is about three feet to two meters, which is about six feet, depending again on the projections that you look into. The most recent one, the one on the bottom, we can see if you follow the red line, it goes up to like one point, maybe two, five meters. And then there's like a range of uncertainty related to all these projections. So anywhere from like three to six feet by the end of the century is what we would expect to see. Again, all of these projections have some sort of, have some uncertainty related to them just because there's so many processes that are hard to predict. We don't know, for example, how much carbon are we going to put out into the atmosphere in the coming years or any other factors that contribute to the rising in temperature and the rising sea level. It's hard to predict. So there's always a number, we always want to know a specific number, we always want to know what is going to be sea level rise by 2050 or by 2100, but in fact, it is very difficult to give a single number and that is why all of these projections have many different paths as to that describes where are the values that are most likely to be by the different years. And I'm sure we could have a whole show devoted to why sea level is rising at all in terms of heating up the ocean and various melting ice sheets. But I think the second slide you prepared would show the viewers a little more graphically what kinds of impact. And I think these four diagrams give us quite a good impression for Eastern Pacific and North America. What are the four images we're looking at? So the four images that we're looking at are four different scenarios. These are from the same paper that the first graph on the top, the first graph that we saw. And this is what I wanted to do with this slide was to show you that even though the projections of global mean sea level rise range from say three to six feet or so by the end of the century, the rate at which sea level is going to rise is going to be different depending on what part of the world you are. And this is because of all the different factors contributing to sea level rise. So for example, we have adding of water into the ocean because of glaciers melting, thermal expansion because the ocean is heating up. But then there's also the land itself that is either rising or lowering because of other unrelated factors. So the rate at which sea level is going to show in the different places is going to be different. In this case, if we look at Hawaii, we can see for example, in the two meter global mean sea level rise scenario that the colors are red. So it will be, which means that by the end of the century, we will have around one meter or so of sea level rise. Whereas if we look at Alaska, for example, there are some blue colors there, which shows us that the sea level is actually going to drop, but this is relative to the land. So all these values that we're looking at here are relative to the land. Yeah, a very complicated situation. So there's no one statement that you can make in terms of globally sea level rise, this amount, all places equally sort of thing. But what kinds of effects can one expect here in Hawaii? Particularly your mass and stasis, I think, look to Waikiki, what kinds of effects would you expect there? And maybe we can look at the third slide, which I think will graphically show. Right, so. I'm familiar with, I recognize quite a few of these, but this is quite serious stuff, right? Right, right, so I'm glad you point that out that these are familiar places. This is what I wanted to accomplish when showing these pictures, is having people relate to this issue that's going to affect all of us. So here in Hawaii, we are already seeing, we can already see cases when the ocean rises more than we were expecting, for example, kink tights, we tend to call them. And what I wanted to show is that even today, we can already see the effects of what a rising sea level could bring to Hawaii. So flooding of the streets, waves breaking over the sea walls. In this case, we have a parking lot that, probably by a marina that is being flooded and a good way to try to analyze these pictures and look into the future and think about what is it that we're going to face is to think about all of these kink tights in the future are going to be a low tide. So if now this is the low tide, what we can start thinking about, well, how is the high tide, how is the high tide going to look if this is already the low tide? Tell me more about what you mean by a kink tide. Obviously, the images you showed were real photographs going back to 2016, but what is a kink tide? Right, so we normally have the normal tights which are predictable. We say, oh, tomorrow the tide is going to be high and it's going to rise, whatever, one feet, two feet, right? But then there's other factors that are background levels of water that affect also the tides, which are a little bit harder to predict, for example, eddies or different currents or storm surge if there's a storm happening at the same time. So usually, I mean, kink tides means that the tide is higher than we had previously expected it to be. So I see, our Sea Grant program at UH got those photographs. They look as if they're from Waikiki and Mapunapuna and I was out at Alamoana beach, for example, on one of those occasions. And yeah, it's disconcerting that there's a lot of saltwater encroachment onto the infrastructure. I actually had a question come in over the chat and I'll read it. So are there construction techniques that can be implemented to address this kind of threat, either for homes or for businesses? What do people do apart from moving land? Right, this is a very difficult question and it depends on what is it that the sea level is going to cost in the specific place that you're trying to put your infrastructure or modify your infrastructure. So say for example, if you're really close to the coast, people would tend to put up sea walls to prevent coastal erosion and to prevent the houses from falling into the ocean, right? But then there's also this other component of places that can be flooded because of the water table rising with the level of the ocean and getting inundated even though they're not connected to the ocean. So it really depends on what is it that you're trying to, what is the issue that you're trying to address? And where you mentioned rising water table, I know your thesis for example, you look at Waikiki and the diagram slide number four starts to look very disconcerting if we could have the fourth slide. This is one of three I think you've prepared for flooding it just over a meter. So that's probably about four feet. About four feet, right? Yeah, and perhaps you can point out, yeah, I can see the alloy canal and... Right. Yeah, so this is the heart of our tourist area. What is it that these are showing this diagram? Right, so in this diagram, we're showing flooding the at least 80% probability of flooding of the Waikiki Peninsula to make these maps. We take into account uncertainties that are related to the data that we use to make this diagram. And that's where the 80% probability comes from. In this map, we can see the Hilton Lagoon is that blue blob to the left of the diagram. And then you can see the alloy canal. The areas that are depicted in shades of blue are areas that we would expect to be flooded and through marine inundation, which means that the area has a direct connection to the ocean. Whereas the other areas that are depicted in shades of green are areas that in the modeling lie below the water level that we were modeling but don't have a direct connection to the ocean. And based on people... How did you produce that map? I mean, do you go out with a surveying equipment or do you have other kinds of data sets that you use? So this is all done by computer. What we do is we use what is called a digital elevation model or a DEM, which tells us what does the terrain look like? What's the height of each specific pixel in this case on our DEM? And then the other part of the simulation is a tidal surface. So where is the ocean relative to our digital elevation model? And what we do is we raise this tidal surface little by little, assuming the different scenarios of sea level rise, say, for example, okay, we have two, three feet of sea level rise. We raise our tidal surface and see what are the areas in our digital elevation model that lie underneath the tidal surface. All of the areas that are underneath the tidal surface then are assumed to be flooded and then after we assume that they're flooded, we can distinguish which areas are going to, would we expect to be flooded directly from the ocean or which areas are going to be flooded by groundwater inundation? So even though this is a simulation, your input data are real and basically elevation measurements as well as land use. And that illustration was hard to believe. That was the good scenario, right? That was just a meter and 1.2 meters. The next slide shows something a little bit more disconcerting. We go to slide five. So this is also by the end of this century, right? So it's the same kind of model, but a higher level of sea level rise. Exactly. So as I showed in the very first slide, there's different paths that we can follow in terms of emissions of greenhouse gas emissions. And all of these paths have an outcome on how much sea level rise are we going to see. And for each one of those paths, I made a different map. In this case, this map shows the somewhat, not the worst case scenario, but a very bad scenario already. In this case, we're looking at 1.9 meters of sea level rise, which would be about six feet by the end of the century. And we can see most of the Waikiki Peninsula is all in shades of blue, which means that the ocean is going to flood the whole, or most of the peninsula by the end of the century. If we were to follow this, one of the worst carbon emissions. And of course, it wouldn't stop, sea level wouldn't stop rising in 2100. And this is just a snapshot in time. But another question over the chat, for example, if you're flooding Waikiki to even a meter, what do you think that means for the economy or the financial health of Hawaii? This is bad news over the thought. Right, right. So this will be bad news and bad news. And I mean, bad news in, from different perspectives, and in all the perspectives, it seems like it's bad news. It would increase coastal erosion. It would obviously flood some areas. Buildings, for example, that have stories, what are they called? Underground will start flooding. The sewage system might be affected. Anything that is really underground and that can be reached by the water table rising is going to be a concern. Is there anything good or positive that can come out of dealing with sea level rise should we make Waikiki a Venice of the Pacific, for example? I know you're not an economist. You're not an architect, but there's a good coastal geomorphologist. What do you think? I think that the positive thing that we can get out of sea level rise and all the issues that we are dealing with is the opportunity for everyone, for people from different areas of studies to come together and start thinking for us, for the community, you and me, that we don't want all of these bad situations to happen. I think it's the opportunity for us to get together and figure it out together and for you, for me and for everyone. So your slide six, I think summarizes some of the impacts if we can go to the next one. And here it's a little bit different, right? This is just the probability. Right. What does that probability mean? Right. So with the methodology that we use to make the maps, we can make two different kinds of maps. We can hold either the amount of sea level that is going to flood still and then vary the probability or we can hold the probability and then vary the flood depth. The first two maps that we showed had at least 80% probability of flooding. In this case, I am showing any flooding at all was the probability of any flooding at all happening with 1.19 meters of sea level rise. So in this case, our probability is telling us how sure are we that the daily highest water level would have the extent that we think. So in this case, if we look, for example, the blue areas, we have at least 80% probability of flooding which means that the areas outside of the blue areas have at least 20% probability of staying dry. So for example, this map will be useful if we wanted to plan to build an infrastructure that could potentially be of concern if it were to flood, right? In this case, 20% or at least 20% probability of flooding would give us that the area surrounding that area has at least 80% probability of staying dry. And that is why it's valuable of these probability maps. Well, I see areas just now of the L.Y. canal, like where the golf course is. I used to live some corner of Eisenberg and Capellani and there's a high probability there. So this is just Waikiki. I think your final slide, slide seven actually, so tries to deal more with Oahu and we've got two different screenshots on web pages by the look of it. Right. So the previous slide is a model that I just developed. I just finished my master's in December and that was the outcome of that modeling. And the idea is to take it to the next level and do it for the whole island of Oahu and for the other islands as well. In this case, in this slide, I wanted to show what are the resources available today that you can access to freely. If you wanted to see what is going to be the extent of flooding caused by sea level rise under different scenarios. So in the left-hand side, I'm showing the PAC iOS sea level rise viewer, which for some islands show only passive flooding and for some other islands show passive flooding in addition to flooding by wave action. And then on the right-hand side, I have a screenshot of the NOAA sea level rise viewer and this is another resource that you can look into if you are trying to see what is going to be the extent of flooding. The PAC iOS sea level rise viewer is specific for the Hawaiian islands, whereas the NOAA sea level rise viewer provides the information for the whole United States. And correct me if I'm wrong, but those maps are predominantly through sort of the ocean rising and lapping over the beach. They don't include what you had done for Waikiki, which would be the water leaking through the ground soil and then forming salt marshes and things like that. Correct, correct. So the NOAA sea level rise viewer does add in some specific places, not as much as the one that I did. So we're getting near the end of the show, NOAA, but what are your plans for living either in Hawaii or Wapanui with the rising sea level? Are you heading for the hills or what would be your plan? Heading for the hills is a pretty safe bet. But I'm just here trying to be one of the people that are going to try to help mitigate the bad situations that we can get out of. And I'm really appreciative that you've come on this show. This is the sort of thing the community here in Hawaii needs to hear many times so we can start planning for the eventualities. But alas, we've come to the end of the show, NOAA. So I'd like to remind the viewers you've been watching Science at Soast. I'm your host, Pete McGinnis-Mark. And my guest today has been NOAA Pahoa, who is a graduate student within the Earth Sciences Department. So NOAA, thank you again for appearing on the show. Scary stuff I've got to admit, but very interesting. So good luck with your PhD and hopefully we'll have you on the show some other time. That's all for now, folks. So please join us again next week where we'll have another summary of research at the School of Ocean Earth Sciences and Technology. So until then, goodbye for now. Thank you so much for watching Think Tech Hawaii. If you like what we do, please like us and click the subscribe button on YouTube and the follow button on Vimeo. You can also follow us on Facebook, Instagram, Twitter and LinkedIn and donate to us at thinktechhawaii.com. Mahalo.