Robinson206: One. Robinson206: It's it's great to be here. I'm: I'm. Very pleased that I managed to make you in person at least some of you. Robinson206: So yeah, i'm a i'm a trace level by Geochemist. I'm. A chemical Robinson206: currently at the University of Georgia Skidway Institute of Oceanography. and I'm anticipating a move to the University of Delaware Robinson206: later this year the timeline for that is still a work in progress. Robinson206: But yeah, I I hope we should be up here sometime later this summer. Robinson206: My talk today is about atmospheric deposition of iron to the surface ocean, and the influence that it can have on ocean by geochemistry. The the image that I put on my title slide is a a satellite photo of a plume of of dust being transported Robinson206: off the coast of of West Africa from the Sahara and out into the Atlantic Ocean. Robinson206: And this image is actually from the year 2,000, and I think it's one of the images that really captured my imagination while I was studying my master's degree Robinson206: about the the way these Robinson206: these mechanisms, by which material can be transported for thousands of miles in the atmosphere Robinson206: before Robinson206: settling into the ocean and and influencing the Robinson206: that the Bijio Comes street thousands of miles away. I've been lucky that I've been able to sort of carry on doing this this research throughout my career so far. Robinson206: So i'm going to start my talk today with an introduction to iron as a autumn micro nutrient Robinson206: in the marine environment. Robinson206: The importance of atmospheric deposition as a source of this element to the ocean. Robinson206: And then I'm going to run through a few examples of atmospheric deposition in in different regions, and how it can influence the dissolve iron concentrations. Robinson206: and ultimately influence marine biology at chemistry. Robinson206: And then i'm going to start focusing a little bit more on work. I've been involved in more recently as part of the Geo-traces project. Robinson206: So I am. Is an essential element for life. Robinson206: It's used in various biochemical systems, including photosynthesis. Robinson206: The image on the left here is a schematic of the photochemical of the sorry of the photosynthetic apparatus of most photo troughs. Robinson206: and I put this up just to highlight the number of iron containing proteins which are great that are involved in this process. so i'm as it absolutely essential for the focus synthesis Robinson206: and for fighter plants, and they need to be able to access iron from their surroundings the the surface ocean. Robinson206: and although I am, is one of the most abundant elements on earth, it has a very low solubility in seawater. Robinson206: And so Robinson206: it's typically present in seawater, in in concentrations of Picomola or an animal levels on the right. I've put a a map showing the distribution of dissolved Ion at a 1,000 meter depth. Robinson206: So I chose this to sort of take away the influence of biological, and Robinson206: I just show that even a 1,000 meters that concentrations, usually less than one animal, a kilogram Robinson206: which is around 50 parts per trillion, so very, very low concentrations of life. Robinson206: When we started getting reliable data for dissolved island measurements in the auction in the 19 eighties. Robinson206: The the low concentrations led to this hypothesis Robinson206: that it was the rate of iron supply Robinson206: that was limiting primary production in the high nutrient of low chlorosal regions. So these are regions where there's Robinson206: relatively high standing stocks of macronutrients, such as nitrate phosphate throughout the year they don't get fully utilized, and it was suggested that it was this fly of iron Robinson206: that was limiting Robinson206: the uptake of of these nutrients in these regions. Robinson206: and this was tested Robinson206: numerous places, using incubation experiments by which bottles of seawater were spiked with Robinson206: varying concentrations of of dissolving Robinson206: These 2 panels show the results of one of those experiments. So the red line Robinson206: that shows Robinson206: the change in chlorophyll concentration on the left in a bottle that Hasn't had any. In addition to it Robinson206: I can see that concentrations are relatively low over a few days. Robinson206: whereas bottles that have had various levels of iron at it so Robinson206: sharp increase in chlorophyll concentrations. Robinson206: and on the right. This shows the nitrate concentrations in what? Robinson206: So where I am is being added. Robinson206: the levels of nitrate go down because Robinson206: there's been further primary production in in those bottles. Robinson206: Things have moved on a good deal since then. This image Robinson206: is a result of a modeling study. Robinson206: It shows areas where I am. Limitation is thought to limit productivity of different vital planks and groups. Robinson206: So that's all shown here. Robinson206: And so you can see that over much of the over large regions of the global ocean Robinson206: it's the supplyline that is thought to Robinson206: to limit primary productivity. Robinson206: if not of all fighter function, then of of certain types. Robinson206: So given that the supply of iron is imposing. Robinson206: the the table here summarizes global supply rates of of iron. Robinson206: and this includes both particular and dissolved. I Robinson206: and most of that input is is dominated by riverine and glacial in books. Robinson206: But both of those are at the Ocean Mountains, and a lot of that particulate material Robinson206: quickly. It settles out of the water Robinson206: and doesn't make it into the the open ocean. A lot of the dissolved input Robinson206: gets lost when there's a changing Robinson206: chemistry from freshwater to seawater. Robinson206: And so a lot of that is all by him Doesn't make it out into the ocean interior. Either. Robinson206: The table also includes height and thermal and off-genic inputs so that's I that's released from the sediments Robinson206: as a Robinson206: as that material gets its its process. Robinson206: Obviously, both of those inputs tend to be from from the Robinson206: bottom of the ocean. And so it's difficult for that. I to get up to surface waters. So i'm. A spheric deposition becomes a very important mechanism Robinson206: to introduce I to to surface. Robinson206: This next image shows Robinson206: the results of a modeling study looking at dust deposition Robinson206: when I say dust. I'm talking about minimal aerosol Robinson206: going back to the the satellite image. This is material. It's carried Robinson206: out to sea from arid regions. Robinson206: a desert such as the shower. Robinson206: and you can see that much of the Robinson206: higher the rates of dust deposition, tend to be downwind. Of. Of these arrangements. Robinson206: The Bravian desert deserts of Central Asia. Robinson206: that's not the only Robinson206: atmospheric supply of I Robinson206: to the ocean can also be introduced by a deposition of volcanic ash. Robinson206: industrial emissions, such as burning of fossil fuels and Robinson206: mythology industries. Robinson206: and also by mastering whether that's clearing of land for agricultural purposes or from wildfires. Robinson206: And so you can imagine in these areas where Robinson206: these are the mechanisms which could become more important Robinson206: when I talk about atmospheric deposition. Robinson206: It's actually 2 separate but late processes. There's drive deposition by which aerosol particles gradually settle Robinson206: from the atmosphere under their own gravity. Robinson206: And then this wet deposition by which those particles get stripped out of the atmosphere by rainfall or by snow or sleet. Robinson206: Both processes Robinson206: carry with them various types of aerosol. Robinson206: and in doing so they carry different elements, including. Robinson206: we carry pollutants. Robinson206: They carry elements associated with the aerosol matrix, as well, for example, aluminium and titanium. Robinson206: Both important parts of mineral dust. Robinson206: and these can be used as tracer for that material. Robinson206: Once that material gets introduced to the surface ocean, they can be a dissolution of a a, a certain fraction of of the elements that it carries into the dissolved phase. Robinson206: When we're looking at, we loss of material from the dissolved face as we get a change in Robinson206: chemistry from the freshwater input to to salt water. Robinson206: And ultimately the fate of that material is that it sinks down through the water column to the sediments Robinson206: from by geochemical perspective. We're interested in how large and variable that input is. Robinson206: we're interested in what fraction of that material can be used by the bioter. Robinson206: And then also, whether that input has any detrimental effects, such as the input of pollutants which can Robinson206: impede rates of primary production. or whether there are any other effects. For example, mineral aerosol is pretty dense material. Robinson206: and so when that gets sort of Robinson206: mixed up with organic material getting Robinson206: increases the density of that material causes it to sink faster. Robinson206: and so that can affect the the rate of transfer of organic carbon from the surface ocean to to the deep ocean. Robinson206: Okay. So the first example that I want to give is Robinson206: focused on the Sahar, the Sagaso Sea and Saharan dust deposition. Robinson206: So the so I guess we'll see is some tropical area of the Robinson206: as you can see it's. Robinson206: receives relatively high rates of dust Deposition, because of this transport of Sahara and Dust Robinson206: I'm. Looking at the of Ian Limitation. Robinson206: It's one of the few areas where I am supply Isn't expected to limit primary productivity of of any photo Robinson206: because of because of this. for the Robinson206: I'm going to talk in particular about Robinson206: the waters around Bermuda. Robinson206: So Bermuda is is where I got my first job in oceanography. It's home to the Bermuda Atlantic Time Series. Robinson206: which is a Robinson206: the Time series. Looking at at the the Ocean water column. Robinson206: It's also home to Tudor Hill Marine Atmospheric Observatory, which is being used for time. Series of aerosol measurements in the past Robinson206: and on the right Here is Robinson206: results from a 6 year time series of aerosol iron concentrations that've been needed. Robinson206: and it's been split up by by months of the year. Robinson206: So you can see there's a very strong seasonal signal Robinson206: a better. So I resulting in the a different Robinson206: transport pathways Robinson206: to Bermuda at different times of the year. Robinson206: So the first project I was involved in Robinson206: involve measuring dissolved iron concentrations at the Bat site in the Time series. Robinson206: This was in the summer of 2,003, Robinson206: and we were interested in the Robinson206: the the influence of saire and dust deposition. So we also measured aerosol samples. Robinson206: So on the left to you. Robinson206: So I am on the right Robinson206: to dissolve that most call. Robinson206: This crew is coincided with a so how many dust events? So we Robinson206: we actually sold Robinson206: relatively high concentrations of aerosol I Robinson206: of around 10 animals permute. Robinson206: and as a result of that event. Robinson206: watercoln surface ocean dissolved at, and concentrations where products we all like around one to 2 animals to police. Robinson206: and we also actually saw a Robinson206: strong increase in dissolved I of around 0 point 6 nanos per litre over the the cost of that 2 recruits. Robinson206: It's part of the same project. We we followed that up with another cruise and the following screen. So this is outside of the dust season. and we Robinson206: so much lower airline concentrations only around, but less than one animal for me to cute. Robinson206: and if the water column profile is all down very different as well Robinson206: the surface there are only concentrations of point, one to point 2, and animals per lit. Robinson206: So this project was followed by another Robinson206: that had basically the same approach. But looking at Robinson206: the dissolved iron profile in that region over an 18 month period. Robinson206: So we started with a cruise in April. 2,007, Robinson206: is it? Before the dusty season? Robinson206: You can see the dissolved iron profile over the offer of 2 or 300 meters is very sort of flat. Robinson206: with lower concentrations of less than 0 point, 2 animals per litre Robinson206: on our next research crews. In the summer Robinson206: those surface concentrations have increased to point 4 to point 6 and animals per litre because of atmospheric Robinson206: dust inputs. Robinson206: I knew that, but sorry. By November we started to see some seasonal cooling of the other ocean. Robinson206: and so the iron concentrations, the Robinson206: similarly high. But that signal had been mixed over the over 80 meters also. Robinson206: We went back out the fall in March. Robinson206: We were back to having this fairly. very flat Robinson206: profile Robinson206: concentrations that decreased a little bit back to point 3, now more to itself Robinson206: as a result of winter mixing and biological drawdown of the iron. Robinson206: and then going back into the imagine light so much Robinson206: so further increases, and resolved back from some directions through some more Robinson206: comes very time. Robinson206: So Robinson206: the reason I wanted to include this was just to show how, in this region the the dissolved iron profile is really controlled by atmospheric inputs. Robinson206: 5 Robinson206: ocean mixing, called like upper ocean seasonal mixing Robinson206: and biological uptake also plays a role in that. Robinson206: The next example is looking at volcanic ash, their position in the highest. Robinson206: This is a region that receives much lower breaks of dust deposition, because it is Robinson206: not directly downwind from any of Robinson206: the bottom Robinson206: figure here shows sea surface nitrate. This is an area Robinson206: that that has residual macronutrients at the end of the spring gloom. Robinson206: It's not a high, nutrient, low, chlorophyll area as such. Robinson206: but it does have some nutrients that I need. Robinson206: I'm looking at the not the fine limitation. Robinson206: It's an area where I'm has the potential to limit small fireplace throughout the and they have been previous studies that show Robinson206: using incubation experiments that show that I can be a link to Youtube. Robinson206: So, as part of my Ph. D. I was involved in a project called Yumja Basin, I study Robinson206: which aimed to improve our understanding of I and biochemistry in this region. Robinson206: We're focused on the ice and basin yourself license. Robinson206: You haven't your base in between. Robinson206: To do this we had research cruises in the spring and summer of 2,010, Robinson206: and the the the plan was to measure these all time distributions throughout the region Robinson206: to quantify potential inputs Robinson206: and but Robinson206: Assess potential and limitation across the region. Robinson206: However, that first cruise coincided with the eruption of a fi Al yoko in southern Iceland. Robinson206: So this option. Robinson206: lastly, for around 4 weeks between mid April and the mid May. Robinson206: 2,010 used to introduce for the Robinson206: the movement of the Robinson206: and then on the right. Here is a satellite image Robinson206: showing the aspirin propagating down to the southeast from some. Robinson206: So this is a fairly high altitude. Robinson206: but it also shows this area of lower altitude. We. Robinson206: where there is wind, blow, and ash being carried out across the license. Robinson206: So this this was actually take on the seventh of May, and I was at sea at the time. We would probably Okay. Robinson206: So we we got very close to this Robinson206: as part of that project. I was responsible for collecting aerosol samples on both cruises. Robinson206: The map here shows where we collected samples. Robinson206: What I each sample started. Robinson206: and the the X's showing where Robinson206: what each one Robinson206: the right ones, if the spring Robinson206: and the blue ones of the summer. Robinson206: and there are so high, and concentrations to show them on the right. This is a walk. Robinson206: so you can see a huge range in the concentrations during the spring from around 10 under the the the southern part of the the study. I Robinson206: if you have to. Robinson206: But then, as we got up to Robinson206: so he's really high Robinson206: concentrations of around 85,000 nanograms per met cute. Robinson206: and by contrast in the summer months concentrations were much lower throughout the region, and less variable. Robinson206: We assess the solubility of the iron in that material, and it was very low with around Point 1. But even so, the sheer amount of material with the deposited to the the region Robinson206: resulted in an increase in dissolved and concentrations. Robinson206: So this map shows distribution of resolved iron in seawater surface sea water. Robinson206: as it says, from tofish samples Robinson206: see Robinson206: far from Iceland's. The concentrations were only around 0 point, 2, 9, Robinson206: and then, as we got closer. so concentrations of up to 2.5 not exploited. Robinson206: not still fairly low. Robinson206: and it may not seem significant. Robinson206: But for a system such as this, where iron can be, the iron supply can be the limiting nutrient. Robinson206: Those differences can be significant. Robinson206: So we use our ash measurements of the the I am content of the solubility of the I am. Robinson206: and we used it with an ash deposition model Robinson206: to assess how that input could Robinson206: effects diss all dying across the entire region because we could only measure a small small area. Robinson206: So this thing that shows the model results for the increase dissolved by what we found was that for around 35% of the Iceland basin. Robinson206: This input increased the dissolved iron concentration by point. 2 and animals to these are all ball Robinson206: over the duration of the eruption. Robinson206: So this next image is a Robinson206: a plot of chloride, a concentrations. Robinson206: 7 by satellite imagery for the region. Robinson206: The black line is for 2,010 our study year. Robinson206: and then the gray line Robinson206: is the climatology for the region on the negotiating Robinson206: that. That's the variability in the climate. Robinson206: So what this is showing is that in 2,010 the of the eruption Robinson206: there was a Robinson206: and earlier than usual spring blue. Robinson206: and that increase in chlorophyll a was much sharper than usual. Robinson206: and then the next clock shows nitrate concentrations Robinson206: in the ice and basement. and again the the blue dots represent. Robinson206: So the climatology. There's a dissolved iron concentrations, measures in previous years. Robinson206: At different times the Red Dogs Robinson206: represent the average concentrations and matrices measured during our cruises in the spring and the summer. Robinson206: and the key thing. Here is Robinson206: the summer nitrate. Concentrations were significantly lower than done for the years. so that residual nitrate that it's shown up on the previous block. Robinson206: There's hardly any nitrate left in the so on. Robinson206: and the conclusion of this is that it was the input of extra dissolved I into the region Robinson206: from ash deposition that it promoted this Robinson206: sharper spring bloom. drawn down nitrate concentrations Robinson206: to a greater extent than than normally curves, so the ash deposition have influenced the bi geochemistry of the region. Robinson206: The third example is a project that I wasn't involved in personally. Robinson206: but it's a more recent example, and I think this study was pretty cool. What the way different datasets were used. Robinson206: This one's focused on the South Pacific. So the notion. Robinson206: So this is an area that generally receives low amounts of dust. Deposition in an area where I am is again considered to be the limiting nutrient. Robinson206: This project was built around a time series of Aerosol Act measures in Tasmania. Robinson206: This is from the period of November, 2,019, to march 2,020. Robinson206: So this comes out with a severe wildfire season Robinson206: in Australia. and this shows the the iron concentrations are shown by the blue blue line. Robinson206: and it is compared to the Indian Robinson206: Paris Ali, and concentrations up on site for the previous 3 years Robinson206: just horizontal. Robinson206: And then the green bars, concentrations of liver glucose in aerosols lever glucose is a biomarker aerosol. Robinson206: Sorry a biomark of molecule Robinson206: that's used as a tracer of wildfire aerosols. Robinson206: What this is showing you this Robinson206: this is higher ever. So I, in concentrations associated with the emissions from from the wildfires that were taking place in Australia. Robinson206: And and what was done in this study is that Robinson206: those aerosol. Robinson206: those those aerosol measurements, were used as a sort of starting point. and then satellite imagery along with models for Robinson206: air, mass trajectories, and dust. Their position. We used to truck that other souls Robinson206: downloading from Australia Robinson206: across the South Pacific Southern Ocean. Robinson206: and then the team focused on this area. Robinson206: So Robinson206: 2 thirds of the way across the the South Pacific. Robinson206: So then they looked at chorus delay concentrations from satellite, and and just Robinson206: in this region. Robinson206: and that is shown by the the green line. Robinson206: and again they compared to climatology for the region. Robinson206: using all the the supply things Robinson206: she's shown by a dash line on the the green shave. Robinson206: So during this period of the wildfire aerosol deposition there was an increase in Robinson206: and colourful, and in that region. Robinson206: under the the black palace that was shown here also satellite data for aerosol optical depth due to black car. Robinson206: So again, that's the tracer of Robinson206: basically so in the atmosphere Robinson206: that that came from these wildfires. Robinson206: and then finally they they again use satellite data to access the Robinson206: the rate of net primary production and export production Robinson206: in that same region during this period of of deposition from Australian wildfires. Robinson206: and related it to the climatology for the region. Robinson206: and what they showed is that there was a small but significant increase in primary production and export production in that area Robinson206: due to Robinson206: I'm. But presumably due to the I'm. Associated with these aerosols Robinson206: that was depositing in those waters. Robinson206: Okay, so what I I hope I've shown to you in these, with these examples is the different. Robinson206: including dust, ash, wildfire emissions. Robinson206: They can transport iron for hundreds and thousands of kilometers from the continents to the remote ocean Robinson206: deposition of that material can influence Robinson206: seawater, dissolved iron concentrations. Robinson206: though they typically remain in the Nanamo range. Robinson206: Those changes in in iron can be significant. Robinson206: and that can influence productivity in the region. Robinson206: And this in places in some places that could alleviate Robinson206: I and stress of of the resident phytoplankton population. Robinson206: Okay. So for the rest of my talk I want to focus on work that I've been involved in more recently. Robinson206: So since moving to Cigarette Institute of Oceanography Robinson206: I've been involved in the Geo. Traces project Robinson206: for those of you that aren't familiar geo-traces is a Robinson206: long-running international project. I think it's been running since Robinson206: around 2,010, maybe a little bit earlier than that. Robinson206: and it it aims to improve our understanding of the biogeochemistry of iron and other trace elements Robinson206: in the in the global ocean. Robinson206: In particular, the AIM is to quantify the different fluxes of of these elements into the ocean. and assess how You' them influences their distribution. Robinson206: Obviously atmospheric deposition is is a part of that. Robinson206: The the math that I'm. Showing here is. Robinson206: and that work of the research cruises that are associated with Geo traces. So the the yellow and the black lines. Robinson206: 1% Robinson206: research cruises at the ballroom being completed and the red ones transact the Robinson206: still plant. I think this is a little bit out of date, but for the most part it represents Robinson206: the the state of of Geo traces. Robinson206: So one of the benefits of of being involved in geo-traces as someone focused on atmospheric deposition Robinson206: is that it? It gives us the opportunities to go out and collect samples in areas that are traditionally undesampled. Robinson206: A lot of the focus on atmospheric deposition historically, has been on the North Atlantic. Robinson206: On this Robinson206: the the large effect that it's aar and dust deposition. That's that. Robinson206: So during my time at skid away. I've been involved in several separate projects. Robinson206: This is the Robinson206: A. Gp. 16 transact of Eastern Pacific Zoneal transact. Robinson206: I didn't go on this cruise myself. but I've I've worked on some of the samples. Robinson206: and what you can see from the Aerosol and Concentrations associated that transact to sort of steep defining concentrations. Does. The ship moves option Robinson206: to the It's a remote Pacific. Robinson206: the very low concentrations. Once we got away once once the ship was away from the Continental margin. Robinson206: My muse to Ste. The way Robinson206: was basically for Robinson206: the next Us. To your traces section, which is the West. Robinson206: So this one took place in 2,015, and the ship left from Dutch, however. and the Lucian Islands went up to the north. Robinson206: back to Robinson206: again the I Robinson206: relatively low I didn't freak out. Robinson206: Point out this data set Robinson206: is this one sample. It is quite a bit higher than the others. This is associated with an Amos of Robinson206: kind of Robinson206: took with it a pulsive of of dust. Robinson206: Then, in 2,018 I was. Robinson206: I took part in the Gp. 15 transact to Pacific. Robinson206: down to Hawaii, then on to Robinson206: this is in September to November, 2,018. Robinson206: Again, iron concentrations and aerosols were relatively low. Robinson206: You can see there is Robinson206: some difference in the 2. It's slightly higher concentrations of the North Pacific and lower concentrations as we got to the equatorial. Robinson206: and then I'm. I'm. Now involved in Gp. 17, Robinson206: which is the next Usg. Address section. This is being split into 2 research cruises. the first of which took place at the end of last year. Robinson206: which one from Robinson206: to he to Chile. We have a student on board that collects the aerosol, Sam Robinson206: for that one. and then I'm. Due to take part in the Gp. 70 a. And T. Then this year. Robinson206: which will focus more on something Robinson206: in such a long time. Robinson206: They're doing aeros or sampling on on transit or Robinson206: benefits and drawbacks. The the benefits is that we take some changes over Robinson206: relatively large Robinson206: spatial scales. Robinson206: Or we're only getting snapshots from from those areas we we sample for 2 or 3 days. Robinson206: Well, generally while the ship is under way. Robinson206: And so Robinson206: the entire data setting maybe covers a couple of months. Robinson206: and it just gives us a snapshot of our concentrations in that region Robinson206: where that becomes more useful is if we're able to compare that data, set 2 ones from the same area at different times in year. That's what I've done in this. The 2 Robinson206: boxes of the shaded reds. Here This is the Gp. 15 data from 2,018. Robinson206: I split it up into Robinson206: North Pacific and Equatorial Pacific. and then I've compared those. Robinson206: There is some I and concentrations Robinson206: paid from from other research crews in the same region. I want you to summarize the topic. Robinson206: So what you can see for the knots is that this this nice seasonal change. Robinson206: how we Robinson206: peak in concentrations in sprint. Robinson206: This is you to Robinson206: transport of mineral aerosol, and and genetic aerosols from Eastern Asia. Robinson206: we'll buy the the 4 months for me. With that Robinson206: the dominant weather weather pattern is different. So we don't get that transport of material. Robinson206: Hence the the lower concentrations. Robinson206: In contrast, the equatorial Pacific Doesn't really show any seasonal Robinson206: seasonal variation. and that's probably because the Robinson206: the Amos transport is is more regular throughout the year, but also because it it isn't down the street don't wind it Robinson206: of any of the major dust sources. So there's lower inputs of AI to the region. Robinson206: So I've been talking mostly about Robinson206: concentrations of our assault iron. Robinson206: This is what we measure. We have these examples, which consist of motor. Robinson206: It it Robinson206: digest the filters. Robinson206: We measure the Ion concentration, and then we relate that to the volume of a. That's P. Through the filters. Robinson206: But what we're really interested in is the deposition looks Robinson206: which is the supply rate from atmosphere to the ocean. Robinson206: and that's related to the concentration by control, deposition, velocity, the the speed at which those particles Robinson206: settled from the atmosphere Robinson206: that's influenced by a number of factors. It's a partial size, meteorological conditions, sea surface roughness. Robinson206: and it's very difficult for us to Robinson206: to measure all of those parameters that in real time Robinson206: out Robinson206: one approach that's commonly used instead is to use literature values for deposition laws Robinson206: such as these 2, Robinson206: where you use a value of point, one centimeters second for fine particles Robinson206: or value of one centimeters; second for course Robinson206: in practice we don't like, say we don't always know the distribution of possible socks. Robinson206: and while this method misses out is we. Robinson206: which is also an important atmospheric deposition, input Robinson206: we do try to measure this during geo-tracism cruises. but Robinson206: it's a very transient feature If Robinson206: If there's a range hour as the ship is underway, we're able to collect a Sample. Robinson206: if it's a mile off to starboard, and we have a Ccd. In the water, we're not able to to go over and and sample that way. Robinson206: So the what deposition looks is is related to the Robinson206: the concentration of the in in rainfall multiplied by the rainfall rate. Robinson206: But it can also you link back to the aerosol concentration Robinson206: multiplied by a scavenging ratio Robinson206: and a correction factor for the different densities of air and water. Robinson206: So both aspects of atmospheric deposition can therefore links to the aerosol concentration. Robinson206: so they can be linked together as a bulk. Deposition flux is equal to the aerosol concentration Robinson206: multiplied by the bulk deposition velocity. But this puts us back to the Robinson206: the area where we need to calculate that deposition. But lost Robinson206: during geo-traces we've done this Robinson206: using beryllium 7, Robinson206: so brilliant 7 is a naturally occurring radio nuclei. Robinson206: It's produced in the upper atmosphere by cosmic rays, striking elements of nitrogen and oxygen Robinson206: and it has a half-life of around 53 days. Robinson206: When those when when brilliant 7 is produced. Robinson206: it rapidly gets scavenged on to only a sole passports in the atmosphere. Robinson206: and then it gets deposited to the ocean Robinson206: by both wet and dry. That position Robinson206: because of the short half-life of its distribution in the ocean isn't strongly affected by ocean currents. And so it's. Robinson206: Basically For the most part it it's just this distribution is controlled by the atmospheric deposition Robinson206: on its own radioactive decay. So this is a typical profile of I. The concentrations in the service mixed layer due to exposure to the atmosphere. Robinson206: and then a sharp decrease in concentrations in deeper water. Robinson206: where the that is not being exposed to Amsterdam. Robinson206: So if we conduct profiles to measure Prism 7 we're able to integrate between those different depth samples I to calculate the infantry Robinson206: and the in the of the. Robinson206: and that is related to deposition, looks. and the decay decay rate Robinson206: from my previous slide. I also said. Robinson206: The deposition flux is related to the aerosol concentration and the book deposition boss. Robinson206: So, by measuring both the aerosol concentration Robinson206: and the surface ocean inventory. Robinson206: and also having knowledge of the decay constant. Robinson206: we're able to calculate a bulk deposition velocity Robinson206: from these beryllium measurements, and then we can apply that deposition velocity to Robinson206: a assault, concentrations of of other elements. Robinson206: This is what we did during Gp. 15. Robinson206: This panel Robinson206: shows a result. Beryllium. 7 activities, concentrations. Robinson206: black dots on along the transact from north to south. Robinson206: white dots that were showing you just the the rainfall Robinson206: that transit from satellite imagery. Robinson206: and I I shared it in this area in red Robinson206: it's just the Robinson206: where there is a sharp increase in rainfall. Robinson206: This next panel shows the the really inventory. Robinson206: which was measured at each of the hydro stations on that transit. And so again, I've shared it in the tropical version. So Robinson206: I've also written these 3 samples. Robinson206: These new stations Robinson206: where the beryllium, 70 country is significantly lower. Robinson206: Of these are stations where equatorial taking place. and so Robinson206: and in that these stations there's deeper water that Hasn't been exposed to atmospheric inputs that's coming up and diluting that beryllium 7 signal. Robinson206: So that means these 3 stations can't really be used to assess at atmospheric inputs. Robinson206: This last panel shows the calculated deposition velocity along the Trans. Robinson206: the 3 your following stations. I just Robinson206: I put in the outreach phone Robinson206: just to to pop the data. Robinson206: What this shows is that Robinson206: this relatively little variability in the deposition velocity along the transact. Robinson206: except within the Robinson206: instruct, the converted zone. Robinson206: where that intense rainfall is more efficient than challenging material from the atmosphere. Robinson206: So, as a result of this data, we were able to calculate 2 Robinson206: average port deposition velocities, one for the instructional convergence zone and one for the rest of the transit. Robinson206: And then those values were applied to our aerosol iron and data to calculate Robinson206: input rates are Robinson206: those input rates are Robinson206: basically seasonal scale averages because of the the nature of Robinson206: William. 7 and it's it's Robinson206: half-life of around 53 days Robinson206: one of the aspect that we're Robinson206: interested in in terms of so atmospheric supply. Robinson206: What fraction of that material is available for biological update uptake. This depends on the residence time of the particles in the upper ocean. It depends on the solubility of the ailments Robinson206: and any other strategies Robinson206: that the biologists can use to access those elements from from the aerosols once they're in the ocean. Robinson206: In practice, what we generally do is use the solubility as a proxy for bioavailable Robinson206: Now, aerosol and solubility measurements range Robinson206: range from point 0, one to 90%, which is quite a big range. Robinson206: That's because solubility is influenced by several factors. It's influenced by the Robinson206: source and composition of the material. Robinson206: For example. Robinson206: aerosols resulting from industrial emissions, tend to have more soluble. Ion associated with them compared to mineral dust. Robinson206: The soy votes is affected by the transport time Robinson206: as aerosols are being transported in the atmosphere. They undergo photochemistry reactions, cloud cycling but through exposure, to to water Robinson206: and interactions with other aerosol types which can affect the solubility Robinson206: it's affected by a possible size due to the changes that has on Robinson206: surface area to volume ratio. Robinson206: but it also depends on our definition of what soluble is. Robinson206: And if you look through the literature, there's a huge range in Robinson206: leaching Robinson206: conditions used when assessing aerosol solubility on the left. Here is a list of different which you most of your water. Robinson206: the 9 late technical reach Robinson206: to acetic acid with a reducing agent, which is much more aggressive. Robinson206: and we also go from relatively rapid exposure Robinson206: of the aerosols to the reagent, to for long exposure, which you would expect would lead to a Robinson206: release of a greater percentage of the iron into solution. Robinson206: So top 2, Robinson206: Compare these different data sets Robinson206: What we did during geo-traces. And as we assess Sol, you're not using multiple methods. Robinson206: so I pointed that in this figure so the block line in here is the total line Robinson206: that was so high concentration Robinson206: from digestion. Robinson206: What we to soluble I so Robinson206: these 2 datasets about from a relatively rapid exposure of the aerosols Robinson206: to a Robinson206: a, a weekly tin agent, showing ocean high security water, and thought of sea water. Robinson206: and then what I can lay by I, Robinson206: which is a more aggressive leach that's expected to Robinson206: potentially mimic Robinson206: What percentage of that I could be released over a longer time scale Robinson206: and comparing the solubility. Robinson206: the fractional. So you go to for those 3 methods. Robinson206: They also feel water and the seawater very, very closely. Robinson206: which Robinson206: suggests that the altar pure water approach is a good proxy for filter Seawater, if we don't have access to to that in in other Studies. Robinson206: whereas the the the led by I Robinson206: fraction of the Robinson206: Fraction is considerably Robinson206: now i'd hope to finish off. When I When I agreed to give this talk, i'd hope to finish up with some science fraction 80 day, or sold data of my own Robinson206: that danger isn't ready to share it. Robinson206: So I've I've used this study from the East China City. which used time, serious measurements of aerosols. Robinson206: 2 different sites. Robinson206: So what's showing Robinson206: these 2 concentrations of Robinson206: different size fractions at those sites? So the on the left are smaller aerosols Robinson206: going to all course larger aerosols on the right dark blue dots is the total aerosol Robinson206: from a digest Robinson206: the red dots. Robinson206: This is this is solid by a parasol iron. So again, this is a fairly weak lynch. Robinson206: and all that terrible in dots Robinson206: is the lay by a line which is again from a more aggressive leaching solution. Robinson206: And what this is showing is that Robinson206: the total line is dominated by a aerosols. Robinson206: But for labile and sole of the I, there's a shift towards finer a sort, so Robinson206: more of that soluble iron is associated with the smaller particles Robinson206: that's again shown. Robinson206: and the percentage solubility by by size, fraction. Robinson206: What I thought was interesting about this study Robinson206: is that they concluded that fine aerosols less than so that the the Robinson206: accounted for around 92% of the soluble iron Robinson206: in in this material. Robinson206: It was the corset aerosols Robinson206: that accounted for most of the difference between labile and soluble. Robinson206: So, although both treatments released a similar amount of I am. Find a sar of salt Robinson206: as you as you got to cost the size fractions, bigger differences between those 2. Robinson206: And so their conclusion was that it's the residence time of the causa aerosols in their surface ocean. Robinson206: and the interaction of those particles Robinson206: with iron binding ligands Robinson206: that plays a critical role in deciding that the total bioavailable high influx. Robinson206: So this study was done like saying, we use China City. This is an area that receives high inputs of both mineral, aerosol. Robinson206: and anthropogenic aerosols. Robinson206: And so I think this is a really interesting conclusion, and it would be interesting to see Robinson206: how this translates to different Robinson206: ocean regions with lower aerosol inputs, or perhaps a different balance of aerosol supply mechanisms. Robinson206: Okay. So my my last slide of Robinson206: I focused on I. It's my my element of choice. But when we make these measurements. Robinson206: you know, we collect the aerosol samples, digest them. Robinson206: and make measurements, usually with a IC. Pms. Robinson206: Without instrument. It's just as easy to measure multiple elements at the same time Robinson206: as opposed to focusing on violence so Robinson206: for all of these Geo-traces projects, Especially I've been generating data for Robinson206: several different lines. Robinson206: So this gives us information about supply rates of other important micronutrients. It also gives us information about some traces of different. Robinson206: So like I said, Stop. Robinson206: Oh, I understand you are both traces of mineral aerosol. Robinson206: The managing is a useful tracer Robinson206: combustion, a results. So yeah, all these numerous different elements associated with. Robinson206: Okay, I'll finish up like with acknowledging Robinson206: some of the people associated with this work. I I've kept the list Robinson206: fairly concise. So Click book is Robinson206: the the lead scientists in the lab where I've been working over the last few years. the landing Dave Carto and and a. U. S. List, for all Pi is on on different Geo. Traces projects. Robinson206: The work that I did in Bermuda Robinson206: was led by Pete Cedric and by Tom Church. Robinson206: I used to be at the University of Delaware. Robinson206: and then the the work that I did in the High High Institute, not the Atlantic. Robinson206: Eric Heckerberg, Richard Sanders and Peter Stathon were I. Ph. D. Advisors Robinson206: and the other people is to grow all play prominent groups. Robinson206: So with that I will take any questions. 4. Cannon 202: I can't see who is in your room. So Cannon 202: here. Yeah. Cannon 202: Yeah. So maybe you can moderate questions up there Robinson206: for sure. Yeah. Robinson206: okay. Robinson206: I don't know this directly, the next input I was wondering Robinson206: any kind of calculations to see. So I imagine, with the Robinson206: anthropogenic ourselves, and you will have an increase of Cannon 202: greenhouse gas to the Robinson206: But then you'll have the deposition Robinson206: and an increase, possibly of productivity and sequestration. Is there any offset Robinson206: this release? I there? Yeah, it's a it's a good question. Robinson206: There is Robinson206: some level of offset, I think so particularly looking at. so so back. Robinson206: so Robinson206: it's like the East Asian Robinson206: a solid mission. This this is a next year of. Robinson206: and that gets transported to the kil, and that gets transported to the kil. That's an unlimited area. Robinson206: So Robinson206: I think there have been some studies that that indicate that Robinson206: those inputs have so relieve iron stress and improve Robinson206: primal production rate. But in terms of Robinson206: you know, offsetting global carbon missions. It's it's Robinson206: the tiny Robinson206: related to that. The the study that was looking at Australian wildfire emissions. Robinson206: I believe it. The conclusion from that paper was that the Robinson206: well, so I I I, that they they calculate the export production. Robinson206: And one of the conclusions was that this effect Robinson206: from deposition in South Pacific, and some offset Robinson206: to the cabin released by the wildfires. But Robinson206: it's it's not a complete offset. You know it just doesn't. But any other questions Cannon 202: anyone here. We have questions on the Cannon 202: what I want to do. Robinson206: Mine's only a comment. Cannon 202: Yes. Cannon 202: this is a very interesting talk, so I wonder so, because you. Cannon 202: Bermuda, study you, you talk about the the mixing. In fact, Basically, the iron concentration is the like Cannon 202: about the next layer. The Cannon 202: not a lot of you started. You only focus on the surface concentration, right? If you're not correctly so, why Cannon 202: so for the North Atlantic area, Why only focus on the surface concentration. Robinson206: So the the focus on on both Robinson206: both projects. It's really Robinson206: the change in the surface mixed layer. Robinson206: So what I was showing in the Bermuda studies Robinson206: was that it's it's the the increase from atmospheric deposition is to the surface mixed layer. But then. Robinson206: in the winter months, obviously. Robinson206: you get deepening of that next layer as the as the air temperature and the water temperature cool. Robinson206: And so that makes sense that I am down Robinson206: over a deeper depth interval. So maybe the up at 2 or 300 meters Robinson206: for the highest to the North Atlantic. Robinson206: That was again, we we focused on the Robinson206: basically the surface ocean. Robinson206: I and change. Robinson206: But that was. Cannon 202: you know we were only there in in the spring and the summer, so we could only Robinson206: really look at how things changed over that, and showed a time period. Robinson206: So i'm not. Robinson206: I would suggest that for the high-lasting north atlantic Robinson206: that I am. But what is all being Robinson206: pretty much used up by by the late summer. and and what else was remaining would have been again mixed over a much Cannon 202: deep part of the water car and the in the winter East. Cannon 202: Does that answer your questions? Yeah. Cannon 202: Because you know the the Nox Atlantic, the Savoor and NASA, that's where it is the region where the North Atlantic Cannon 202: deep water formation. So if i'm green those those are the surface with your tongue, and Cannon 202: like a transport it to the sun. And what is the resonance time for the Cannon 202: you know, for the like. Cannon 202: like 170 years. Cannon 202: the global Robinson206: Yeah, I can't tell you. Cannon 202: So yeah, I Robinson206: I think so that this this influence from the Robinson206: Okay, ash. Robinson206: I think that that's a signal that would have. Robinson206: So basically. Robinson206: It's fairly trans it. It was an input of I in the spring that I am gets used up. Robinson206: And and then so what would have been incorporated into Robinson206: particular material sort of sunk out of the the upper ocean. Robinson206: so i'm not sure that much of that would have really being mixed down in the winter months to to the deeper Robinson206: the water as as dissolved. Now. Cannon 202: Okay, thank you. Robinson206: Back to my comment. Yeah. Robinson206: On the Icelandic volcano. It's a sort of very transient, temporary Robinson206: seemed almost instantaneous. Robinson206: Yes. Robinson206: yeah, I I Robinson206: case this. Robinson206: this eruption happens to take place. Robinson206: So just around the time. Robinson206: gearing up to to make use of almost pregnant. So it's Robinson206: with this. Robinson206: So it's really important that Robinson206: focusing on that them supply by Robinson206: happens Robinson206: in the system where. Robinson206: on nutrient stress. Robinson206: which was the case here. You know this upstanding stock of micronutrients that available to coincided with Robinson206: sort of calmer conditions as more somewhat. So it it all just comes together to Robinson206: promote the the spring. Robinson206: Just another question. Who couldn't understand that from the Robinson206: I find it? Volcanoes and Robinson206: i'm deep into the water column. Did you take measures? Robinson206: We we conducted profiles down. Robinson206: I think this is typically to a 1,000 meters. But on some occasion Robinson206: this is Robinson206: like to within 100 people. Robinson206: And in Robinson206: Yeah, I I only showed the the so tofish samples. Robinson206: So the Robinson206: the dissolved I am signal. What I remember Robinson206: it was. It was only evidence in the Cannon 202: And so Robinson206: basically. The surface next point Robinson206: below that you don't. Robinson206: The reason why I was asking is it's a pretty exotic location that is the north of. So I was wondering if the Robinson206: vertical transport rates were different Robinson206: at that exotic location relative to other more boring locations. Robinson206: The Robinson206: Us. Transport rates or the yachts for the apprenticeship with the signal show up at a 1,000 meters much more quickly the Robinson206: at this time of year I I would say no. Robinson206: certainly, for the dissolved face. Oh. Robinson206: for the the majority of the materials from staying up to the place Robinson206: 6 steps Robinson206: We did some particular by invasions German Robinson206: that's sprinkled with cruise, and Robinson206: but only down to about 2, so you can see it at the stations near the blue. Robinson206: Hi. but Robinson206: I would imagine we would see that if it would. But Cannon 202: we have some questions from Zoom. If we can jump in. Robinson206: yeah, go for it. Cannon 202: So i'll read the first one. So the question is from Andrew Wozniak, and he says, i'm curious about the aerosol size data that you were able to put together quite yet. What are those samples from. And do you have any expectations about how those labile dissolved? Total iron trends will differ among Cannon 202: biomass versus biomass burning versus mineral dust? Sources? Robinson206: Yeah, good question. So the the data device Robinson206: Don't have ready to go. Robinson206: It's actually Robinson206: it's size fractionated aerosol data from 3 different Geo traces. Robinson206: The specific zone transact Robinson206: civic Meridianal transact on the Western Arctic section. Robinson206: I have the Robinson206: total digest data for all all 3 of those datasets. Robinson206: and I have. Robinson206: I've applied the same chemical leaches to those samples as well. Robinson206: Those are the samples that are currently waiting to be run on the icps. Robinson206: and i'm really just wondering. Robinson206: But I don't have that day to to show what I Robinson206: I mean. What I anticipate is that the the finer aerosol size fractions are more soluble. Robinson206: Oh. Robinson206: similar to to what we're seeing in this subject. Robinson206: All of those samples that I collected are fairly remote. Robinson206: And so there's obviously a Robinson206: atmospheric process in component as well. And so I suspect that Robinson206: the differences in size structure won't be Robinson206: it's pronounced it. Robinson206: The the numbers for the cost-size fraction will be how you Robinson206: that is shown here, so it will be less difference between fine and Cannon 202: and then trying to do you want to unmute and ask a question? Cannon 202: We can hear you. Okay. Chandranath Basak: Yeah, I Well. Chandranath Basak: good. Chandranath Basak: I'm: trying. Yeah. Okay, yeah. Great Great Doc, I My question is kind of following what? And it's asking. So if I remember correctly, you did some leaching experiments on the sample from the middle of the transact, right Chandranath Basak: where you use the filtered seawater versus normal di water to look at the the fraction that is coming. Is it again? I I I might be wrong. But is it that you're seeing the same kind of leaching effect on both of these treatments on all of the samples as you go along the meriden of Transit. Okay. Robinson206: So I mean what those? So what those 2 Lynches show is that this is very low functional solubility. Only one or 2% along the entire transact. There's a little peak in solubility. Chandranath Basak: Yeah, yeah. Robinson206: But Robinson206: and that that's the the concentration there, but it's also seen in the fractional sustainability. Robinson206: and that's in the North Pacific. So this Robinson206: is potentially associated with a slightly higher conjugation of Robinson206: So, as I said at this time of year, that's not Robinson206: that that transport of antigenic aerosol from Asia isn't as high. Robinson206: but it's Robinson206: it's going to be higher than it is in the Robinson206: So I think I think this summer it's like Robinson206: teaching in higher solubility is is probably associated with that Robinson206: we've given some sub samples to a team that look at personal isotopes. So i'm going to be able to pick out a bit more data Robinson206: related to that. Chandranath Basak: Yeah, I mean that that was. That was what I was going to ask is that if you, if you just disregard the the anthropogenic component. Chandranath Basak: the source of these a results also vary along that that transact right. So so that means you are fundamentally getting very different samples. So if you lead them. Chandranath Basak: I would expect it to behave a little differently even with you know, a filtered seawater. So that's what kind of that's what I was probably getting at. Is that? Chandranath Basak: How is that you don't really get anything out as you're leaching them with seawater? Robinson206: It's a good question. Robinson206: I mean. So in in terms of the sea water, you know it's only going to be. You're only going to keep as much time in solution as as possible. Robinson206: Take my position by Ligands Robinson206: could have some influence the Robinson206: the exposure time of of the material to the leaching. This is very short for this procedure. It's only a Robinson206: that's Robinson206: because it's all pretty well. Robinson206: Yeah, I mean It's it's kind of a shame that you don't see Robinson206: more interesting. Robinson206: Go ahead Robinson206: that that that's the way it is. Robinson206: It looks out. Robinson206: Yeah, I not sure what else to say is that? Chandranath Basak: No, no, that's that. That's that's great. What I was wondering if I know These samples are extremely valuable, and you probably sample limited. But in a in a similar future experiment, is it? Is it worth doing a longer time like you? You harvest every 30 s, and see how it Chandranath Basak: how the the concentration changes with time. Would that something be more informative in terms of this experiment, that the way you have set it up. Robinson206: Do you mean the Robinson206: different exposure time? Robinson206: Yeah. Robinson206: Yeah, that that that would be a good experiment to do, I think Robinson206: I know. So I a reference for literature, and how variable these Robinson206: reaching experiments on Robinson206: I know there are. There are some studies that have done Robinson206: separate allequops of what's pure water? So they Robinson206: they they leach, we at 50 mile of water. Robinson206: and then they another 50 mail, and and compare, and what it jen one, it generally shows is that Robinson206: most of the material comes off in that first alliance. Robinson206: And then there's a sort of big step down. We still get some. Robinson206: some I and release the next couple. So yeah. Robinson206: it's a it might be a good thing to test. Actually. Robinson206: I see how we are Chandranath Basak: sure. No, thank you great, great, great talk. Thanks. Cannon 202: Thank you, everyone for your engagement, and thank Chris one more time. That breakfast.
Chris Marsay - SMSP Spring Seminar Series 2023
From Taylor Link April 28, 2023
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"Atmospheric Deposition of Iron and Its Influence on Ocean Biogeochemistry"
Chris Marsay
Chemical Oceanography
University of Delaware
Zoom Recording ID: 98935302803 UUID: veg7P+gLQx6Ch+rKbHGFnw== Meeting Time: 2023-04-28 03:01:31pmGMT
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