FALL 2025
Wednesdays at 3:00 pm, Seminar Room SLAB 103 / Virtual SLAB 103
Aug 20: Dr. Givo Alsepan
Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee
A Potential Pathway for AMOC Influence on Seasonal Atmospheric Variability
The importance of Gulf Stream (GS) variability for Northern Hemisphere weather and climate has received considerable support in recent years. Recent observational advances show that significant GS variability occurs on multiple timescales, including seasonal. Recently, a high degree of seasonal variability has also been observed in the Atlantic Meridional Overturning Circulation (AMOC), suggesting a potential connection between the seasonal AMOC and mid-latitude atmosphere via the GS. Modeling studies, however, are yet to agree on the exact relationship between AMOC and GS variability, partly due to the lack of eddy-scale resolution. Here, a novel ensemble of eddy-rich model simulations is used to investigate the patterns of co-variability between and fine-scale sea surface temperature (SST) anomalies over the GS on seasonal timescales as a function of time lag. Our results reveal that wintertime variability in GS SST and its meridional gradient are preceded by AMOC variability in the previous summer. These AMOC-induced SST gradient anomalies then drive air temperature gradient anomalies through changes in the differential air-sea sensible heat flux. The findings indicate a potential pathway through which deeper ocean circulation precedes atmospheric variability via the GS. The identification of this pathway may provide a potential source of untapped predictability in weather forecast and climate prediction systems.
Aug 27: NO SEMINAR
Sep 03: NO SEMINAR
Sep 10: NO SEMINAR
Sep 17: Dr. Lisa Beal
Department of Ocean Sciences, Rosenstiel School
More Eddying in Subtropical Western Boundary Currents is
Cooling Adjacent Shelf Waters, Warming Surface Waters Downstream,
and Reducing Oceanic Meridional Heat Transport
Lisa Beal1 and Kathryn Gunn2
1Department of Ocean Sciences, University of Miami, 2University of Southampton, UK
Recording Available at COMPASS ON DEMAND
Observations indicate more ocean eddies with climate change, especially in swift boundary currents like the Gulf Stream. Eddying drives cross-shore fluxes of heat, salt, and nutrients that impact the current and the adjacent shelf-sea environment. Yet, it is unclear whether more eddies will tend to warm or cool the current, suppress or stimulate coastal ecosystems. To approach this question, we study Agulhas Current instabilities off South Africa, quantifying their cross-shore eddy heat and salt fluxes for the first time, using two years of continuous mooring data. We find that eddies converge heat and salt towards the current core over time. On the inshore edge, 10-km frontal instabilities dominate eddy fluxes, pumping cold, nutrient-rich waters up onto the shelf and producing a net offshore heat flux. Farther offshore, 100-km meanders drive net onshore fluxes of heat and salt. Together, these instabilities yield a broader, more stratified Agulhas Current that transports more surface warmth, but less total heat, to higher latitudes. Turbulence closure theory predicts these same tendencies for subtropical boundary currents globally. Combined with greenhouse-driven surface warming, our findings imply that coastal ecosystems will face stronger extremes in future, with cooler more productive bottom waters alongside warmer more deficient surface waters.
Sep 24: Dr. Cassandra Gaston
Department of Atmospheric Sciences, Rosenstiel School
The Impact of Dust and Beyond on Marine Biogeochemical Cycles
Aerosols supply key nutrients, such as phosphorus and iron, to receptor ecosystems that can stimulate primary productivity and, consequently, lead to carbon sequestration in the ocean and terrestrial biosphere. This so-called "aerosol indirect biogeochemical effect" has not been studied as well as the direct radiative properties of aerosols or aerosol-cloud interactions. Mineral dust has been assumed to be the most important contributor of nutrients to receptor ecosystems. However, nutrients in dust can be present in poorly soluble forms leading to several outstanding research questions including, what processes are most important for transforming insoluble nutrients into bioavailable forms? and are non-dust aerosols more important than dust for the delivery of bioavailable nutrients? To answer these questions, we combined traditional, bulk chemical analysis from aerosol filters with state-of-the-art single particle methods to obtain mechanistic information as to what processes are most important for driving aerosol nutrient solubilization. The results from our work have challenged current hypotheses regarding dust aging as well as the importance of dust aerosols in driving biogeochemical cycles. I will present several works exploring chemical processing of dust thought to increase nutrient solubility as well as nutrient delivery from non-dust sources including volcanic ash and smoke from wildfires. I will also discuss the major sampling platform used to conduct this research, the Barbados Atmospheric Chemistry Observatory (BACO), its recent upgrades, and future directions for research at this site.
Oct 01: SPECIAL ATM & OCE FACULTY PRESENTATION SERIES
Dr. John van Leer
Department of Ocean Sciences, Rosenstiel School (retired)
My Life as an Oceanographer, Engineer & Advocate – So Far
As I plan for the next 20 years of my – all-electric – robotically assisted life, it's time to reflect upon my previous 85 years. I grew up during WW2 before TV, web, or AC, with Victory Gardens and Gold Star Mothers and Wives. By 4, I knew I would be a scientist or engineer – thanks Smithsonian. I attended National Geographic Lectures at 7. By 14, I designed and built a homemade SCUBA (Self-Contained Underwater Breathing Apparatus) and had my first tank filled at WHOI. By 15, I was an apprentice machinist. At 16, I was the youngest Fuller Brush Salesman. In high school I raised tropical fish and built drag racing cars commercially.
I graduated Case BSME '62, worked on Reentry Inertial Guidance System design / testing at MIT Instrumentation Lab, MINUTEMAN-MIRV for 3.5 years. I graduated from MIT–WHOI Joint Program in Oceanography '71, studying Shear & Density Gradients in Thermocline Microstructure under Henry Stommel. For the following 51 years, I was in the RSMAS faculty, designing, building, and using the first robotic oceanographic profilers – Cyclesondes, including solar-powered telemetry. As an observational oceanographer, I participated in multiple West Florida Shelf Experiments, CUEA (Coastal Upwelling Ecosystems Analysis) experiments – two in Oregon and two in Peru – and tropical oceanic observations during the Global Atmospheric Research Program's Atlantic Tropical Experiment (GATE). I participated in six months of under-ice observations in the Marginal Ice Zone Experiment (MIZEX) and the Coordinated Eastern Arctic Experiment (CEAREX) during the Cold War, as well as an over-winter under-ice study of the roll structure in the bottom boundary layer near Copper Harbor in Lake Superior.
As UM faculty, I taught over a hundred graduate students and over a thousand undergraduate students, with first-hand knowledge gained during four and a half years at sea and two decades of lobbying the US Congress for carbon pricing legislation. I served as Vice Chair of the School Council during the Berman years and Chair of the Marine Committee and UNOLS Representative. I also headed the Calanus Replacement Committee during the Rosendahl Deanship, helping raise $0.5M from the Nason Foundation to construct an efficient catamaran ship with the first robotic motion isolation system, described in my first COMPASS Seminar.
Oct 08: Dr. Marybeth Arcodia
Department of Atmospheric Sciences, Rosenstiel School
Oct 15: Dr. Jeremy Klavans
Department of Atmospheric Sciences, Rosenstiel School
Oct 22: SPECIAL ATM & OCE FACULTY PRESENTATION SERIES
Dr. Roland Romeiser
Department of Ocean Sciences, Rosenstiel School
Oct 29: Eric Mischell
Department of Atmospheric Sciences, Rosenstiel School
(one-hour ATM student seminar)
Nov 05: Tyler Tatro
Department of Atmospheric Sciences, Rosenstiel School
(one-hour ATM student seminar)
Nov 12: Aidan Mahoney
Department of Atmospheric Sciences, Rosenstiel School
(one-hour ATM student seminar)
Nov 19: William Downs
Department of Atmospheric Sciences, Rosenstiel School
(one-hour ATM student seminar)
Nov 26: NO SEMINAR (Thanksgiving Recess)
SPRING 2026 PREVIEW
Jan 14: Dr. Lauren Zamora
NASA Goddard Space Flight Center, Greenbelt, MD / University of Maryland College Park
Guest of Paquita Zuidema, Department of Atmospheric Sciences
Feb 18: Dr. Andrew Dessler
Texas Center for Extreme Weather, Texas A&M University, College Station
Guest of the Department of Atmospheric Sciences
