 OK, our next presenter is Nish Etige from Boston University. Nish's presentation is titled, Influence of Large-Scale Currocio Extension Variability on the Pacific Decadal. OK. I'm going to start that again. Nish's title of his presentation is Influence of Large-Scale Currocio. I think I said that right. Extension Variability of the Pacific Decadal for Session and the High-Resolution Version of the Community Earth System Model or CESM. PS, Nish is going to be a daddy. Thank you, Ben. All right. So, hi all. I'm Nish Etige. I'm from Boston University Department of Earth and Environment. I'm a doctoral candidate over there. And today I will be presenting my work on Influence of Large-Scale Currocio Extension Variability on the Pacific Decadal Precession in the High-Resolution Version of the Community Earth System Model. I know it's a handful, but I will just let you know what's crucial extension and Pacific Decadal Precession in the background. So what you are seeing in the picture is a map of surface ocean currents in the world. And if I use my power, I can use the pointer. So you can see these ocean currents are wind-driven. And on the surface, my focus area is on the Currocio region of the North Pacific Ocean, Ocean's Western Boundary region, where we have this particular current called Currocio Current. And before the extra tropics, it moves towards the Central Pacific Ocean as an extension where we call this the Currocio Extension, which is the ocean current. And so when it comes to Currocio Extension, as I said, it is the eastward extension of this subprovacal gyre. And what this Currocio Extension do is it brings a lot of warm water from the equatorial region to the northern regions. And while bringing this, this has shown a periodicity, a quasi-decadal periodicity in terms of sea surface height and sea surface temperature. So that is a basic overview on Currocio Extension. And then moving from the Currocio Extension, like moving from the North Pacific Ocean to the North Pacific Atmosphere, in North Pacific Atmosphere, people have seen a phenomenon called Pacific Decadal Precession, another term which was in my title. And so this Pacific Decadal Precession is a 10-year counterclockwise progression of an atmospheric pressure dipole, which is a high-pressure pattern and a low-pressure pattern, as you see in the picture. And what happens to this pattern over the years is this progresses, this circulates among each other. And as you can see, it clearly shows a North-South dipole pattern at one phase, which we call the North-South teleconnection phase and an East-West teleconnection phase at one point. And these different phases of Pacific Decadal Precession, or PDP, has been linked into changes in environment, such as marine heat waves in North Pacific, cold air outbreaks in the Eastern United States, drought conditions in North America, terrestrial heat waves over the Western United States, and much more. So as I said, Croatia have a Decadal Variability. And Pacific Decadal Precession, as its name says, has a Decadal Variability. So people have asked the question before whether Croatia have to do something with PDP, because they are both in the same oceanic basin or atmospheric region. So in order to answer that question, my advisor, Bruce Anderson, looked into what kind of cause-effect Croatia and PDP have. In his research, he has found that PDP, both forces and response to the variability in the Croatia extension, sets a feedback loop. So for an example, as you can see here, the heat fluxes of Croatia sets up the PDP pattern, and later on, the Westward propagation of these pressure patterns and the resulting wind stress anomalies supports a Baroclinic Rossyby wave, which propagates Westward and modifies the crucial heat flux. So it keeps happening in a 10-year period. So this is the basic of my doctoral work. And for that, to further dig into the teleconnection stage, I wanted to answer the question, like what kind of variability of Croatia sets up the PDP or modifies the PDP or causes the PDP in the North Pacific region? So based on that background, my three chapters of my doctoral dissertation has been created. And these are my three research questions that I try to answer in my doctoral dissertation chapters. So my first question I try to answer is what scale of Croatia extension variability influences the downstream atmosphere that causes the Pacific Decadal Precession? And while looking into my first chapter, we saw some kind of link between Croatia extension and marine heat waves. So my second question I tried to answer was, what is the influence of Croatia extension variations on marine environmental extremes in the Northeast Pacific Ocean? And then my third question, I will talk more about that question. But the third question is, how does the Croatia extensions influence on the North Pacific atmosphere? And marine environments change as the global climate changes, my colleagues. All right, so I will give you a brief overview of how I answered my first question and second question before going to the third question. So to answer the first question, what scale of Croatia extension variability influences the PDP or North Pacific atmosphere? What we did was like we used reanalysis data from OSTIA and NOIR-60, as well as ERA-5 for atmospheric data and the Interpencar Reanalysis data. So all these are reanalysis data. And so in that work, we found that the non-dominant mode of the second mode of large-scale Croatia variation extension sets up a meridional SST gradient, as you can see here. And this meridional SST gradient supports ocean heat fluxes supporting a North-South dipole-like pattern, which is similar to PDP. And later on, the modifications said done to the jet and the sonar propagation of stationary wave energy, this dipole supports another pressure-monopole downstream, which you can see here barely, and which supports the east-west phase of the PDP or Pacific Decadal Precision. All right, so that is a basic understanding of my research question. And also, trying to answer the second research question, we have seen that that large-scale variability of Croatia also supports sea surface temperature anomalies in the Gulf of Alaska region in the Northeast Pacific, which is similar to the recent marine heat wave event that we observed in year 2014 and 2015, which we call the Blob. And so this is a basic overview of my second research question. So when it comes to these two research questions that I tried to answer, an obviously obvious question in the present world, which you all talk about these climate change and emissions and all these different climate change scenarios, the obvious question that we have now is how does these crucial extensions influence on the North Pacific atmosphere and marine environments change as the global climate changes? So this summer at ENCA with my mentor, Annalena Depamaya, we tried to lay our groundwork to start answering this question. So for that, we used high-resolution CESM data. We looked into two outputs, a control output where there is no forcing, and a historic output, which runs from 1878 to 2007 to determine how this mentioned association that we have seen using reanalysis data is present or whether they are present or not in the Croatia extension and present or not in these models when it comes to Croatia extension and North Pacific atmosphere links. So basically, the data have a resolution of 1 fourth of a degree in the atmosphere and 0.1 degree of the ocean. And let me take you all through the methodology that we used. So what we did was we took the PI control and historic output, and then the high-res CESM SSD was low-pass filtered because we already know the large-scale variability is the reason for these PDP-like patterns in the North Pacific atmosphere. And then we subset the Croatia extension region. We conducted an EOF analysis, took the second EOF because it is a non-dominant EOF in the CAI index, and we regressed the peer control and historic related atmospheric diagnostics as well as ocean diagnostics onto the Croatia extension index. And so then this is what we got. So with regards to the CAI indices, so these are the two CAI indices that we produced of the Croatia extension indices that we produced in the PI control and the historic output. And as you can see, these two EOF patterns also have a similar pattern of the meridional gradient, or meridional temperature gradient in both PI control and the historic output. So all right. So then once we regress the ocean and atmospheric diagnostics, we first regress the sea surface temperature, as you can see here. And I'm just keeping this pre-analysis output for sea surface temperature here so we can compare. As you can see, in both historic and PI control CSM outputs, we see the meridional gradient. Even though there are slight differences in the PI control and the historic output, but we see the meridional gradient which supports the North-South pressure dipole pattern. And when it comes to the lower atmosphere or 850 hectropascal heights, we see some kind of dipole, but the southern portion is a bit weak in the PI control. But when it comes to historic runs, we see the dipole as well as the downstream high-pressure pattern. And then this is the upper atmosphere because the response is baroclinic equivalent. We see the same pattern as we observed in the reanalysis data. Moving forward, so we further looked into surface heat fluxes, how the corrosion extension induces surface heat fluxes. Here, the shading is positive downward, where that means a blue color means heat to the atmosphere. So supporting heat to the atmosphere supports always a high-pressure system and vice versa. And then what we have seen in our reanalysis data is this dipole pattern sets up a straight jet and blocks when it comes to reanalysis. It blocks the northward heat transport. So if you take a look at the meridional heat transport or the northward heat transport, it blocks the meridional heat transport in this region supporting the low-pressure system. And also when it comes to the downstream, it supports northward meridional heat transport, which supports a high-pressure system. But unfortunately, this is still not co-locates very well with the high-pressure system. But this is a thing that we further need to study. All right, so if you summarize my work, summarize my presentation, what we have seen is large-scale variations of the corrosion extension, causes pressure patterns over the North Pacific and North America. These patterns are north, south, and east-west phases of the Pacific decadal procession. Also, there is a link between the corrosion extension variations and marine heat waves in the Northeast Pacific. This causes a link, so observed in ocean and atmospheric reanalysis. And what we did here at NGAUs, we conducted initial investigations to determine whether these links are present in the high-resolution CESM model outputs. And then, so upon that work, we have seen that K-Ecosis atmospheric dipole patterns observed in the reanalysis are also present in the high-res CESM PI control and historic outputs. So why this is very important? Because in the future, we are going to continue this work to investigate how the future of K-E and PDP relationship happens to this relationship in a changing climate. And then, we will also investigate the corrosion extension and marine heat wave causality in a changing climate. So with that, I would like to thank my mentor, Dr. Annalena and Dr. Maya, if I think I am OK. And then, my doctoral advisor, Professor Bruce D. Anderson from Boston University, and Dr. Fred Castrocio, Dr. Hukim, and Dr. Justin Small at NGAU who provided us data and supported different insights and feedback on this work, an ocean section of climate and global dynamics lab of NGAU. And for NGAU for high-performance computing support. And Jiti Sakoni for all the support he provided while doing an internship with a different time of my life. And for Alia and Ben for all the support and my NAC colleagues, and also my loving wife, Manu, for supporting me while expecting our first child. Thank you, sir. Thank you. Questions? Hi, great talk. Really important to work. Two questions. I'm not an atmospheric scientist, but I'm a machine learning person. How do you establish causality at a high level for systems like these? Yeah, actually. I'll ask my second question later. OK. So that's a great question, so I haven't shown this. So basically, we did, let me go back, OK. So in this work, basically, we used atmospheric dynamics to see if, OK, so this is not the only sea surface temperature and the geopotasial height are not the only dynamics that we looked into. So we looked into multiple dynamics, such as northward heat transport, heat fluxes, as well as mid-dional stationary wave energy. So when we do that, we established the causality in two ways. First thing is we did lag regressions. When we do a lag regression, we were able to tell the corrosive courses that atmospheric diagnostics. And at the same time, also in our original work on answering the research question one, we used causality analysis, particularly analysis called Granger-Causage Analysis, where we generated a monopole index, especially for the downstream patterns. And then we conducted that analysis to see which region of the sea surface temperatures in the ocean causes this monopole index. So we found that it is the crucial region. OK, so second question. When you say regressions, that means you're rolling PDE systems forwards and backwards kind of thing? Yeah, yeah. Yeah, cool. Thanks. Thank you, Nish, for this presentation. I'm curious. I don't know if you've looked at all at other like oscillations, like specifically the one that came to mind was like the Pacific North America, the PNA. I know it oscillates on a little bit of a smaller timescale, but I'm just curious if you've looked at that at all or thought about that. That's a great question. Even Anna had that question when I started it. Yeah, so basically, when it comes to PDP, I think I missed telling that. So this North-South teleconnection phase is mapped onto North Pacific oscillation. And the East-West teleconnection phase is mapped onto circum-global teleconnection pattern, which is kind of like a regional propagation of waves. But in the case of PDO, things like Pacific Decadal oscillation and so we have taken these indices and like we have tried doing lead-like correlations with this to see if there is some kind of link with this crucial variable. But we haven't found, we haven't seen any strong correlation. So we think like this crucial variability is a variability which occurs by itself instead of forcing from and so PDO. Thank you. You're welcome. Sorry. Great work. I just have a very generic question. I'm wondering if you have any thoughts on how this Kero-Shio extension would change in the changing climate now that that's going to be your next step. That's a great question. Work have, there have been like several work like, I think like there are multiple schools of thought like just like what happens to AMOC, Atlantic Meridian multi-decay, Meridian-Lover training circulation. For Kero-Shio also like there are studies that which says Kero-Shio can weaken particularly or strengthen but depending on the Kero-Shio variability itself. So that is why we should look into like different climate models to see how this Kero-Shio variability will change. But basically work has been done and like seen there are multiple ideas like telling it can weaken in terms of the flow or it can strengthen in terms of the medieval gradient. Great talk, Nish. Thank you. What do you have looked at the differences in the PR control and the historical run? Like what do you think about those? I mean they look a bit different. Yeah, it's true. CO2 forcing is not that strong in the historical run yet. So what do you think about that? This is still work ongoing. I still haven't looked into it. But yeah, I agree with what you are telling. Like there are differences. And so one thing we are trying to analyze is like taking the PI control and historic piecewise way. Like for an example, this PI control this runs for like around 400 years. Instead of like looking at the whole 400 years, like let's take like 50, 50, 50 or 100, 100, 100, taking a look at like why, whether there is a phase where this weakens or like strengthens. And we can do the same thing to historic. But we still haven't done that in the past. Fantastic work, Nisha. Thank you. Thank you so much.