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Greetings from Colombia — Bringing the field to the lab! This photo was taken on July 7, 2025, at the CIMEX Laboratory at the National University of Colombia (UNAL) in Medellín. This space brought together two artisanal miners from Chocó and undergraduate and graduate students from the United States (Southern Methodist University and Colorado School of Mines) and Colombia (UNAL), all collaborating on a joint research project titled Socially and Environmentally Responsible Engineering for Enhancing Livelihoods Within Mining Communities.

The miners shared with us their ancestral method of gold recovery using plant-based mucilage—a local alternative to mercury use. Building on this knowledge, the students will carry out laboratory tests to characterize the process, highlighting the importance of local knowledge in engineering design and contributing to the visibility of sustainable artisanal and small-scale mining practices.

Estuaries: Confluence of the Good, the Bad, and the Ugly

Hello AGU,

Situated at the terminus of watersheds, estuaries function as hotspots of productivity, biodiversity, and human settlement. Estuaries also serve as sentinels of climate and human-induced changes throughout their air and watersheds. 

Muskegon Lake, a drowned river mouth estuary in the Laurentian Great Lakes basin, is a highly productive estuary that boasts one of Michigan’s best fisheries. Other less savory features of Muskegon Lake include challenges common to urbanized freshwater bodies: legacy of pollution, eutrophication, bottom water hypoxia, and nuisance blooms. Over the last two decades, water quality in Muskegon Lake has improved, thanks to restoration efforts reducing nutrient runoff from the watershed. However, in recent years (2021, 2022, and 2024), we have experienced record-breaking nuisance blooms which are dominated by Microcystis sp., the most common toxin-producing bloom-former (its toxin, microcystin, causes liver damage) in freshwater. This is due to warmer waters and an extended growing season, combined with highly irregular and patchy rainfall that failed to flush out the blooms. 

Here, one of us (undergraduate student, Bridget) is tracking the dynamics of Microcystis in Muskegon Lake by regularly taking plankton tows and microscopically documenting its abundance. So far, we are surprised by the unusually early appearance of Microcystis (in April 2025). Perhaps we are heading into a high-bloom, toxic summer, which could compromise the quality of water and life in this otherwise idyllic lakeside getaway.

Greetings from Utqiagvik, Alaska!

In this photo, undergraduate student researcher Bryce Pappas is shown checking on his self-built microcontroller-based multiwavelength spectroscopy sensor. Bryce built and deployed his sensor both at our university and in Utqiagvik as part of the year-long Arctic Geophysics Research Experience, in which students design, build and deploy their self-built environmental/geophysical sensors. He is atop a snow mound looking towards the rising sun over the North Salt Lagoon in early March, 2024. He deployed his sensor well before the sun rose, and it collected data every ~2 seconds for several hours. Using the geometry of our sun's location in the sky, along with a simple model of Earth's atmosphere, he analyzed the data to study atmospheric light extinction for 18 different wavelengths. By observing small fluctuations in the extinction coefficients for certain wavelengths, he inferred the likely passage of a cloud of micrometer-sized particulates unseen by our eyes.

Utqiagvik is a beautiful place with many stunning phenomena such as this "sun dog." Bryce and the rest of our group of undergraduate researchers - and their advisor! - were mesmerized by these occurrences. This image shows two arcs located 22 degrees on either side of our sun, along with a vertical sun pillar. These are caused by flat, hexagonal ice crystals in the air. Their horizontal orientation leads to refraction causing the two side arcs and reflection causing the vertical pillar.

At times like this, after ensuring that a polar bear had not chewed on his sensor in the pre-dawn hours, it was time to stop and just be in the moment, standing quietly in the presence of this amazing sight.

Changing the Face of the Earth: Mar de Plásticos on Land  

Hola AGU,

Spanning over 350 square kilometers in southern Spain, the plastic-covered greenhouses of Almería, densely stacked between the Sea and the Sierra, rank among the most recognizable human-made features on the planet (as illustrated in this NASA Earth Observatory Landsat image from space). Closer, on-the-ground photos from March 2025 reveal an unprecedented industrial-scale use of abundant Mediterranean sunshine, elevated greenhouse temperatures, and modern technology for intensive agriculture. Here, the yield of fruits and vegetables is maximized through the controlled application of water, fertilizer, and pesticides – resulting in 3 to 7 crops per year valued at over 2 billion euros in the global market. 

Almería’s Mar de Plásticos is a striking example of how the “Greenhouse Effect” is exploited to boost agricultural productivity at any cost. While it has increased agricultural yield in this arid region, it has also led to unsustainable groundwater extraction, and exacerbated loss of natural vegetation and topsoil as more erodible areas in the foothills of the mountains are leveled to make way for ever-expanding greenhouses. The extensive scale of plastic pollution affecting the air, water, and soil – over 30,000 tons of plastic waste is generated each year – alongside the impact on regional water quality from fertilizer and pesticide runoff and salinization by saltwater intrusion, as well as their implications for human and wildlife health remain poorly quantified.

As decades of industrial-scale agriculture have overshadowed sustainable farming, the vast Mar de Plásticos has inadvertently transformed the Earth’s landscape. 

Shelf Ice Gift-Wraps the Great Lakes Shoreline in the New Year  

Hello AGU,

Vast expanses of seasonal shelf ice are a prominent feature of polar oceans, with enormous consequences for marine food webs and the temperature-ice/snow-albedo feedback on Earth’s climate. 

            Large temperate lakes, like the Laurentian Great Lakes (~250,000 km2), also experience considerable winter ice cover, which influences shoreline morphology, lake ecology, and regional weather. Shelf ice shields shorelines from storm erosion, provides shelter for fish eggs, affects evaporation, regulates regional weather (e.g., lake-effect snow), and impacts shipping. The annual maximum ice cover (AMIC) on the Great Lakes has fluctuated greatly over the past 52 years, ranging from 12-95% (average AMIC ~43%; https://www.glerl.noaa.gov/data/ice/). While the lakes still experience high ice years (2014, 2015, 2019), there is a concerning trend of a 0.5% yearly decrease in AMIC in synch with warming waters.

            This year (2025), ice cover on the Great Lakes appears to be affected by a relatively colder La Niña winter in the Midwest and the southward push of the Arctic Polar Vortex in early January and mid-February. These events lasted several days and led to rapid shelf ice buildup, as shown in this January 29, 2025, image from Grand Haven, MI, along the western shore of Lake Michigan. As of this writing (in late February 2025), ice cover on the Great Lakes is ~50% – exceeding last year’s 16% AMIC, a year marked by near-record low ice during a warm 2024 El Niño winter. 

There is an urgent need to understand the complex forces shaping the consequential dynamics of ice on water and the fast-disappearing cryosphere in a warming world.

Greetings AGU,

Hello from New Haven, Connecticut! My name is Aline Maybank and this photo is from my recent visit to the Connecticut Department of Energy and Environmental Protection (CT DEEP) air quality monitoring site, where we colocate our ground-level air quality sensors. Here, my lab make Jun Jiang and I are setting up a new batch of PurpleAir sensors to colocate with the CT DEEP air quality sensor. These sensors will soon be given to sent off to communities across the Northeast U.S., so we can expand our public ground-level monitoring network!

Excited to hear from you all,

The Burren: Western Ireland’s Glaciokarst Landscape 

Dear Eos, 

The Burren, meaning “rocky place”, in Irish, is an extensive limestone-based landscape of ~500 Km2 along the western coast of Ireland. The Burren stretches from the offshore Aran Islands (visible from the coastal Lowland Burren pictured here in this September 2024 photo), several kilometers inland to the Upland Burren. Arguably, one of the finest examples of glaciokarst formations in the world, part of The Burren constitutes Ireland’s Burren National Park and the UNESCO Burren and Cliffs of Moher Geopark.

            The Burren formed during a succession of sedimentary rock formations (largely limestone that is hundreds of meters thick) during the Carboniferous Period (~325 mya) and contains a multitude of marine invertebrate fossils – including brachiopods, crinoids, corals, sponges and ammonites – that were fossilized when this part of the paleo-ocean’s sea floor was in the tropics. Today, mysteries abound here both above and below ground. Over time, erosion of the limestone bedrock and successive glaciation-deglaciation scouring, formed an intriguing mosaic of habitats: cliffs, cracks, crevices, caves, ephemeral water bodies such as bogs, fens and wetlands, and even subterranean rivers that still flow episodically.

            Inhabited by humans since Paleolithic times (there is evidence of ~6000 years of habitation), The Burren’s modern-day biodiverse flora (containing 75% of Ireland’s native flora and correspondingly diverse fauna) have been shaped by a confluence of temperate oceanic climate, mosaic of micro-habitats (including scrubland, woodland and grassland), and humans. Grass and scrub vegetation grow amidst cracks in the limestone and local farming practices seek to achieve sustainability through winter-only low-intensity livestock grazing within shifting fenced areas. With its rugged, varied, and irresistible landscape, The Burren continues to inspire visitors and hikers, and remains a thriving center for traditional Irish literature, music, and art...

Gaging an Underwater Waterfall

Dear AGU,  

Ground water venting from sublacustrine karst sinkholes in the Laurentian Great Lakes has unique properties: high dissolved salt (including sulfate) from wafting through Paleozoic marine evaporites, low oxygen due to microbial respiration during the long sub-terranean transit, and a low and steady millennium-average aboveground temperature of ~9oC. At the Middle Island Sinkhole (Lake Huron), groundwater that is denser than the overlying lake water fills the bottom of a ~23 m deep, 10 m wide bowl-shaped nearshore sinkhole. It then spills over the bowl’s sill at ~14 m into the amphitheater-like wider lake floor that is at ~ 25 m – a vertical drop of ~9 m – as an underwater waterfall! Here, the high-sulfur, low-oxygen waterfall – whose flow rate is yet to be quantified – nurtures a dynamic photo- and chemosynthetic microbial mat world. 

            To deepen our understanding of this underwater waterfall (other than the fun fact that divers could have fun sliding down the fall), we deployed 2 tilt-meters (Lowell Instruments TCM-1) equipped with a 3-axis accelerometer + magnetometer for continuously logging flow rate and direction: one at the edge of the sill and the other in the middle of the fall (inset) – already leaning in the direction of flow. Wonder what secrets the time-series data will reveal when we retrieve the tilt-meters next year: Is the flow steady or erratic? Do peak flows coincide with overland precipitation events? Are flow rate and mat growth in synch? How vulnerable are mat ecosystems to the vagaries of groundwater flux as the climate overhead changes?

Harnessing Mountain Water Towers: Mail from Machu Picchu

Dear AGU,

The first thing that impresses those who trek up to the ruins of Machu Picchu – other than the spectacularly biodiverse transition landscape between the Peruvian Andes and the Amazon Basin – is that you are not really on top of the world. Machu Picchu (Old Mountain, in Quechua), located at ~3,000 m above mean sea level, is itself surrounded by towering mountains that rise to ~4,000 above msl. Over 600 years ago, the Inca harnessed natural springs originating at higher elevations to supply water to their homes and irrigate their terraced fields here in this mountain-top sanctuary. In these images from July 2024, one can see evidence of canals crisscrossing the ruins that eventually drain to the Urubamba River in the Sacred Valley below. Evidence of active aqueducts, fountains and irrigation canals can be also seen in the nearby Inca villages that have been continuously inhabited over the past several centuries. One good example of such indigenous hydroengineering lies in the village of Ollantaytambo that has water derived from Andean glaciers perennially running through it. 

World over, people have utilized mountain water towers as a source of water for millenia taking advantage of the power of the water cycle to raise water, the capacity of mountains to store it, and force of gravity to release it – maintaining fertile landscapes of running fresh water. The Romans and Moors have left lasting legacies of their extensive network of aqueducts and canals throughout the Mediterranean – some of which are still functional. 

Today, roughly half of humanity depends on water derived from rapidly dwindling mountain water towers – many of them still glaciated or periglaciated. With anthropogenic land-use changes in mountain habitats altering their capacity to hold and release water, and ongoing global warming accelerating glacial mass loss, water security will get precarious over time. The world’s mountain water towers need immediate protection from the multi-pronged threats eroding their unique water-holding capacity. 

A Metazoan Visitor in a Microbial World

Dear AGU,  

Life in submerged karst sinkholes in the Laurentian Great Lakes, where salty groundwater with high-sulfur and low-oxygen is actively venting, is almost exclusively composed of prokaryotic microbes, Bacteria and Archaea, that build colorful benthic mats capable of both photosynthesis and chemosynthesis. Aerobic organisms such as eukaryotic invertebrates and vertebrates are usually excluded from these isolated underwater benthic habitats (ranging anywhere in size from a room to a football field) due to the prevailing low-oxygen conditions.  

Exceptions abound though. Diver-collected mats and observations from the fringes of these ecosystems, where the groundwater’s influence is diluted by mixing with well-oxygenated lake water, often reveal a host of eukaryotic protists (e.g., diatoms) and low-oxygen-tolerant invertebrates (e.g., nematodes and tardigrades), and even small vertebrate fish (e.g., gobies). However, it is quite uncommon to find larger mobile fish, such as this Burbot (Lota lota, a member of the Cod family, native to inland waters of North America), in the center of the sinkhole in low-oxygen groundwater. Like human divers, fish may be transient metazoan visitors to this otherworldly microbial world. Modern-day sinkholes with actively venting high-salt, high-sulfur, low-oxygen groundwater remain microbial refugia – providing a glimpse into life’s early salty, sulfurous and anoxic microbial origins.

Summer Blooms Trouble Great Lakes Estuaries

Dear AGU,

A cocktail of blooms made up of potentially toxin-producing cyanobacteria (Microcystis sp. and Dolichospermum sp.) has now proliferated for over 2 weeks in Muskegon Lake, Michigan – a Great Lakes estuary. Muskegon Lake is one of two dozen drowned river-mouth estuaries in West Michigan that flow into Lake Michigan – a Laurentian Great Lake. Because estuaries occur at the end of their watersheds, they integrate signals of climate change and anthropogenic perturbations from across their water and airsheds.

Water quality in Muskegon Lake has been improving for over a decade (as indicated by a time-series buoy observatory www.gvsu.edu/buoy/), and restoration measures resulting in reduced nutrient inputs from the watershed have been credited for the lake’s recovery. However, recent years (2021, 2022, and now 2024) have witnessed record-breaking blooms due to warmer waters initiating earlier spring onset and later fall overturn compounded by highly variable precipitation/river loading. This summer, there are reports of intense cyanobacterial blooms like those in Muskegon Lake coming from several adjacent coastal estuaries (e.g., Mona Lake in the South, and White Lake in the North) – suggesting this is a region-wide phenomenon and that current restoration efforts are inadequate to address the long-term impacts of ongoing change.

            Around the world, rivers, lakes and estuaries serve as vital water sources for humanity, biodiversity and ecosystem function. A warming climate and anthropogenic nutrient pollution coupled with more extreme hydrological cycles could turn these waters green and toxic – compromising ecosystem health, water quality, and overall quality of life.

Hello from Utqiagvik, Alaska in late February of 2024! This picture was taking during my year-long biennial Arctic Geophysics undergraduate research class. The students in this class choose their own research area dealing with the sea ice, and then I work with them to build - to MacGyver! - their own microcontroller-based sensors to collect data to address their research question. Most students are there for one of two weeks, with half the class the first week and half the second. One or two of the students are there for both weeks, depending on their particular project. The trip is in late February/early March, when the sea ice is thickest.

This picture was taken one evening when the aurorae put on a particularly spectacular display. We were staying in a dormitory located off the northern end of the grounds of the former Naval Arctic Research Laboratory (NARL), which is itself just north of Utqiagvik. This had fewer street lights than the main NARL grounds, and afforded amazing views of these celestial fireworks. This picture shows one of my students on top of a snow/ice pile just behind (inland side of) the building, caught up in the moment of seeing this phenomenon. He had no idea that I was behind him for this picture, and I was fortunate to capture him howling with his rock hammer in his "hammer of the gods" moment. His unbridled joy is apparent at viewing our sun's deadly particle stream being turned into these harmless and beautiful high-atmosphere light displays by a happy conspiracy of Earth's magnetic field and atmosphere, and leaves an indelible impression. 

In addition to experiencing these bucket-list auroral marvels, my students get the chance to do research under difficult conditions in an extreme environment, so often surprising themselves at what they can accomplish. So many of them refer to this experience - both the research and living in that beautiful area - as "life-changing," and I can honestly say the same thing myself.

What is the age of groundwater venting at submerged karst sinkholes?

Dear AGU,  

Mysteries abound regarding ground water composition, inventories and fluxes. This is particularly true for the age of ground water venting from submarine and sublacustrine vents such as the submerged karst sinkholes in the Laurentian Great Lakes. Currently, we have no idea if the groundwater venting out of nearshore and offshore sinkholes in Lake Huron is days, years, centuries, or even many millennia old – even though this know-how is key to understanding aquifer recharge and turnover, assessing its contribution to lake levels and the potential for groundwater contamination and its transfer to the lake’s interior.

            Here onboard NOAA’s R/V Storm, divers have just brought up groundwater samples in airtight Van Dorn bottles from the bottom of Middle Island Sinkhole (~23 m depth). Working underneath the shade of an umbrella, research technician Tony Weinke and graduate student Cecilia Howard are carefully draining the groundwater samples into copper collection tubes that will be sealed without bubbles and exposure to atmosphere for sulfur hexafluoride (SF6) measurements. Since anthropogenic SF6 arose about 70 years ago, its presence or absence in venting groundwater will inform us if it is relatively young or quite old, respectively.   

Sink or Source? Quantifying Carbon Flux in a Great Lakes Estuary 

Dear AGU:

Occurring at the land-water interface, Earth’s estuaries, are hotspots of carbon cycling.  Muskegon Lake is a highly productive urbanized estuary that drains the 2nd largest watershed in Michigan into the 2nd largest Laurentian Great Lake – Lake Michigan. Our aim is to quantify the carbon flux in this dynamic ecosystem through experiments and time-series measurements that track changes in oxygen concentration (as a metabolic proxy for equimolar changes in carbon) in the lake. Here, graduate student Kaylynne Dennis is collecting surface water to fill clear and dark bottles and redeployed in the lake over a full diel cycle to gage the daily rates of photosynthesis and respiration, respectively. Biweekly experimental measurements will be complemented with seasonal ship-board and continuous time-series measurements of oxygen concentration by the Muskegon Lake Observatory (www.gvsu.edu/buoy/). How will river loading, thermal stratification, wind mixing and algal blooms impact in-lake carbon metabolism, and what effect will the ongoing El Niño conditions have on the net carbon balance of this estuary? What bearing will these findings have for estuaries elsewhere – and the global carbon cycle?

Dear AGU,

My family and I spent summer riding our bikes along the Terrapin Nature Trail, overlooking the marshlands and tidal pools of the Chesapeake Bay. This is home to several species of plants and wildlife.

The scenic Cross Island Trail is perfect for taking citizen science data with the GLOBE Observer app, using its four protocols: clouds, mosquito habitat, land cover, and tree heights.

In a few days, we will be using the Eclipse protocol to record temperature before and after the annular solar eclipse on October 14, 2023, and the total solar eclipse on April 8, 2024.

Greetings from the River of Gold in Colombia!

This photo del Río Nechí or Río de Oro (River of Gold) was taken on July 6, 2023, in the municipality of Zaragoza in Antioquia, Colombia. This river is the cradle of vast biodiversity, but it is also one of the most polluted in the country due to mining activities and the use of mercury. My doctoral research seeks to document and characterize the use of local plants by artisanal miners in gold recovery with my advisor, Dr. Kathleen Smits. In Colombia, this ancient mining practice has been ignored for years and could represent an environmentally responsible alternative to mercury use in artisanal and small-scale gold mining (ASGM). Highlighting the importance of local knowledge in formulating engineering projects, we can contribute to more sustainable mining in the country.