About

Harvey Seim is a professor in the Department of Earth, Marine and Environmental Sciences at the University of North Carolina at Chapel Hill. His research focuses on observational physical oceanography, operating observing platforms to measure physical properties in the ocean, atmosphere, or lakes. He pursues analyses to improve understanding of the fluid dynamics of the sampled environment, employing a variety of autonomous observing technologies such as bottom moorings, meteorological buoys, underwater gliders, and high-frequency radar. He also participates in shipboard sampling efforts. On campus, his activities are largely devoted to analyses, which can be descriptive, empirical, or testing simplified models against observations.

Research topics

• Geography
• Environmental science
• Biology
• Geology
• Geomorphology
• Zoology
• Ecology
• Geometry
• Physical geography
• Demography
• Fishery

Selected publications

• Drivers of Marine Phytoplankton Diversity and Connectivity in the Galápagos Archipelago Spanning an <scp>ENSO</scp> Cycle

  Environmental Microbiology · 2025-07-01

  article

  The Galápagos Islands are a biodiversity hotspot, largely due to the Equatorial Undercurrent (EUC) which supplies nutrient-rich waters to the euphotic zone and supports enhanced levels of primary productivity performed by phytoplankton. Understanding phytoplankton responses to changing environmental conditions is crucial for regional conservation and management efforts. Research cruises conducted between 2014 and 2022, spanning a major El Niño event in 2015 and a La Niña event in 2022, observed varying oceanic conditions and diverse phytoplankton community composition. At most EUC-influenced stations, larger-sized phytoplankton groups (≥ 5 μm) were dominant while warmer, oligotrophic sites favoured smaller-sized phytoplankton groups (< 5 μm). Predictably, nutrient supply was suppressed during the El Niño event associated with the weakening of the EUC and deepening of the thermocline. Counterintuitively, nutrient levels were not significantly enhanced during the La Niña event likely because increased stratification between the mixed and deep water layers reduced entrainment, particularly at Eastern stations. Protist community composition was evaluated using 18S rRNA gene metabarcoding; the majority of detected OTUs were associated with upwelling conditions prevalent around the archipelago. Taxonomic variability reflected heterogeneous environmental conditions generated by the convergence of multiple ocean currents. These results highlight the dynamic interplay of physical and biological factors shaping primary productivity in the Galápagos marine ecosystem.

  PublisherDOI

• Phytoplankton Exhibit Diverse Responses to Different Phases of Upwelling in the California Current System

  Environmental Microbiology · 2025-06-01

  article

  Eastern boundary upwelling currents are some of the most biologically productive and diverse regions in the world's oceans. Driven by equatorward winds and Ekman transport, surface waters are transported offshore and replaced by cold, nutrient-rich deep waters that seed extensive phytoplankton blooms. Studying phytoplankton community succession and physiological acclimation during the initial stages of upwelling is critical to building a comprehensive understanding of phytoplankton responses to upwelling in these important regions. Additionally, factors like lateral transport, seed population dynamics and physiological and molecular shifts are conducive to shaping the community assemblage and primary productivity. This study examines how phytoplankton gene expression and resulting physiology change between early and later phases of upwelling. By incorporating metatranscriptomic analyses and stable isotope incubations to measure nutrient uptake kinetics into our assessment of early and later upwelling stages, we observed variability in phytoplankton assemblages and differential gene expression of phytoplankton that were de-coupled from their physiology. We show that the gene expression response to a fresh upwelling event precedes their physiological response. Ultimately, understanding how phytoplankton change through the course of an upwelling event is critical to assessing their importance to regional biological rate processes, trophic systems and resulting biogeochemistry.

  PublisherDOI

• Effects of Sea Ice on Arctic Delta Evolution: A Modeling Study of the Colville River Delta, Alaska

  Journal of Geophysical Research Earth Surface · 2024-09-01 · 4 citations

  articleOpen access

  Abstract Seasonal sea ice impacts Arctic delta morphology by limiting wave and river influences and altering river‐to‐ocean sediment pathways. However, the long‐term effects of sea ice on delta morphology remain poorly known. To address this gap, 1D morphologic and hydrodynamic simulations were set up in Delft3D to study the 1500‐year development of Arctic deltas during the most energetic Arctic seasons: spring break‐up/freshet, summer open‐water, and autumn freeze‐up. The model focused on the deltaic clinoform (i.e., the vertical cross‐sectional view of a delta) and used a floating barge structure to mimic the effects of sea ice on nearshore waters. From the simulations we find that ice‐affected deltas form a compound clinoform morphology, that is, a coupled subaerial and subaqueous delta separated by a subaqueous platform that resembles the shallow platform observed offshore of Arctic deltas. Nearshore sea ice affects river dynamics and promotes sediment bypassing during sea ice break‐up, forming an offshore depocenter and building a subaqueous platform. A second depocenter forms closer to shore during the open‐water season at the subaerial foreset that aids in outbuilding the subaerial delta and assists in developing the compound clinoform morphology. Simulations of increased wave activity and reduced sea‐ice, likely futures under a warming Arctic climate, show that deltas may lose their shallow platform on centennial timescales by (a) sediment infill and/or (b) wave erosion. This study highlights the importance of sea ice on Arctic delta morphology and the potential morphologic transitions these high‐latitude deltas may experience as the Arctic continues to warm.

  PublisherOA PDFDOI

• Observations of Shelf‐Ocean Exchange in the Northern South Atlantic Bight Driven by the Gulf Stream

  Journal of Geophysical Research Oceans · 2023-07-01 · 7 citations

  articleOpen access

  Abstract Between Florida and Cape Hatteras, North Carolina, the Gulf Stream carries warm, salty waters poleward along the continental slope. This strong current abuts the edge of the South Atlantic Bight (SAB) continental shelf and is thought to influence exchange of waters between the open ocean and the shelf. Observations from a pair of instruments deployed for 19 months in the northern SAB are used here to examine the processes by which the Gulf Stream can impact this exchange. The instrument deployed on the SAB shelf edge shows that the time‐averaged along‐slope flow is surface‐intensified with only few flow reversals at low frequencies (&gt;40‐day period). Time‐averaged cross‐slope flow is onto the SAB shelf in a lower layer and off‐shelf above. Consistent with Ekman dynamics, the magnitude of lower‐layer on‐shelf flow is correlated with the along‐slope velocity, which is in turn controlled by the position and/or transport of the Gulf Stream that flows poleward along the SAB continental slope. In the frequency band associated with downstream‐propagating wave‐like meanders of the Gulf Stream jet (2‐15 day period), currents at the shelf‐edge are characterized by surface‐intensified flow in the along‐ and cross‐slope directions. Estimates of maximum upwelling velocities associated with cyclonic frontal eddies between meander crests occasionally reach 100 m/day.

  PublisherOA PDFDOI

• Extreme seasonal water-level changes and hydraulic modeling of deep, high-altitude, glacial-carved, Himalayan lakes

  Scientific Reports · 2023 · 4 citations

  • Geology
  • Physical geography
  • Environmental science

  Abstract Himalayan lakes represent critical water resources, culturally important waterbodies, and potential hazards. Some of these lakes experience dramatic water-level changes, responding to seasonal monsoon rains and post-monsoonal draining. To address the paucity of direct observations of hydrology in retreating mountain glacial systems, we describe a field program in a series of high altitude lakes in Sagarmatha National Park, adjacent to Ngozumba, the largest glacier in Nepal. In situ observations find extreme (&gt;12 m) seasonal water-level changes in a 60-m deep lateral-moraine-dammed lake (lacking surface outflow), during a 16-month period, equivalent to a 5 $$\times 10^6$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mn>6</mml:mn> </mml:msup> </mml:mrow> </mml:math> m $$^3$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow/> <mml:mn>3</mml:mn> </mml:msup> </mml:math> volume change annually. The water column thermal structure was also monitored over the same period. A hydraulic model is constructed, validated against observed water levels, and used to estimate hydraulic conductivities of the moraine soils damming the lake and improves our understanding of this complex hydrological system. Our findings indicate that lake level compared to the damming glacier surface height is the key criterion for large lake fluctuations, while lakes lying below the glacier surface, regulated by surface outflow, possess only minor seasonal water-level fluctuations. Thus, lakes adjacent to glaciers may exhibit very different filling/draining dynamics based on presence/absence of surface outflows and elevation relative to retreating glaciers, and consequently may have very different fates in the next few decades as the climate warms.

  PublisherOA PDFDOI

• MODELLING THE EFFECTS OF SEA ICE ON ARCTIC DELTA MORPHOLOGY

  2023-03-01

  articleSenior author
  PublisherDOI

• Gokyo Lake 4 temperature and pressure records

  Zenodo (CERN European Organization for Nuclear Research) · 2023-03-14

  datasetOpen access1st authorCorresponding

  Temperature and pressure time series collected in Gokyo Lake 4, in Sagarmatha, Nepal, between June 6, 2018 and September 1, 2019. A taut-line mooring held 9 HOBO temperature loggers bounded by 2 pressure sensors at the top and bottom of the mooring. Matlab files hold each dataset (pressure, temperature) separately. dt variable is Matlab date time, and sensor depths are in centimeters above bottom.

  PublisherDOI

• Extreme seasonal water-level changes and hydraulic modeling of deep, high-altitude, glacial-carved, Himalayan lakes

  Research Square · 2023-03-21

  preprintOpen access

  Abstract Himalayan lakes represent critical water resources, culturally important wa- terbodies, and potential hazards. Some of these experience dramatic water- level changes, responding to seasonal monsoon rains and post-monsoonal drain- ing. We present in situ observations of extreme (&gt;12 meter) seasonal water- level changes in a 50-m deep lateral-moraine-dammed lake (lacking surface outflow), during a 16-month period, equivalent to a 5x106 m3 volume change annually. Data were used to construct a hydraulic model, which was used to estimate hydraulic conductivities of the moraine soils damming the lake. A higher moraine-dammed lake exhibits similar fluctuations. These lake levels lie above the nearby glacier surface. Several other lakes in the region exhibit minor seasonal water-level fluctuations, but each discharge through a surface outflow and lie below the glacier surface elevation. These results indicate that adjacent lakes may exhibit very different filling/draining dynamics and have different fates in the next few decades, based on presence/absence of surface outflows and elevation relative to retreating glaciers.

  PublisherOA PDFDOI

• Cold-Water Coral Reefs of the Southeastern United States

  Coral reefs of the world · 2023-01-01 · 2 citations

  book-chapter
  PublisherDOI

• Atmospheric forcing of the Hatteras coastal ocean during 2017–2018: The PEACH program

  Dynamics of Atmospheres and Oceans · 2023-03-31 · 2 citations

  articleOpen access

  The Hatteras coastal ocean is centrally located along the east coast of the 48 contiguous United States, offshore of Cape Hatteras in a complex land/ocean/atmosphere region where major ocean currents of differing temperatures and salinities meet and interact, where the atmosphere fluctuates on a wide range of time scales, and where atmosphere-ocean interactions vary both spatially and temporally. The Gulf Stream current typically leaves its contact with the continental margin here. Continental shelf currents from the north and from the south converge here, resulting in a net shelf-to-ocean transport of shelf waters that carry important water properties and constituents. The two major drivers of these shelf currents and exchanges are the atmosphere and the oceanic Gulf Stream. Atmospheric driving of the Hatteras coastal ocean is through surface wind stress and heat flux across the air-sea interface. The complexity and importance of this region motivated the NSF-sponsored PEACH research program during 2017–2018 (PEACH: Processes driving Exchange At Cape Hatteras). In this paper, we utilize the substantial number of observations available during PEACH to describe the atmospheric forcing of the ocean then. Atmospheric conditions are described in terms of two seasons: the warm season (May to mid-September), with predominantly mild northeastward winds punctuated by occasional tropical cyclones (TCs); and the cool season (mid-September through April), with a nearly continuous, northeastward progression of energetic extratropical cyclones (ETCs) through the region. Cool season ETCs force the region with strong wind stress and ocean-to-atmosphere heat flux episodes, each with a time-scale of several days. Wind stress fluctuation magnitudes typically exceed mean stress magnitudes in each season by a factor of 3–5. These stresses account for just over 40% of the total current variability in the region, showing the wind to be a major driver of the ocean here. Atmosphere-ocean heat flux is typically into the ocean throughout the warm season (~100 W m-2); it is essentially always out of the ocean during the cool season (~500 W m-2 or more). New results herein include: southward intraseasonal oscillations of the jet stream’s position drove the strongest ETCs (including one “bomb” cyclone); and during the 41 years leading up to and including PEACH, the season-averaged number and strength of atmospheric cyclones passing over the Hatteras coastal ocean have shown little long-term change. Looking ahead, the NSF Pioneer Array is scheduled to be relocated to the northern portion of the Hatteras coastal ocean in 2024, and the NASA SWOT satellite has begun its ocean topography mission, which has a ground-track cross-over here.

  PublisherDOI

Recent grants

• Collaborative Research: Mechanisms of nutrient input at the shelf margin supporting persistent winter phytoplankton blooms downstream of the Charleston Bump

  NSF · $688k · 2010–2015

• Collaborative Research: An Observational and Modeling Study of the Physical Processes Driving Exchanges between the Shelf and the Deep Ocean At Cape Hatteras

  NSF · $1.4M · 2016–2023

Frequent coauthors

• Mike Muglia

  Center for Coastal Studies

  53 shared

• Catherine Edwards

  44 shared

• Dana K. Savidge

  34 shared

• John M. Bane

  University of North Carolina at Chapel Hill

  33 shared

• Lu Han

  China Earthquake Administration

  32 shared

• Ruoying He

  North Carolina State University

  32 shared

• Robert E. Todd

  Woods Hole Oceanographic Institution

  28 shared

• Magdalena Andres

  Woods Hole Oceanographic Institution

  27 shared

Education

• PhD, Oceanography

  University of Washington

  1993