The Department of Geology and Geophysics (G&G) conducts research into a wide variety of topics aimed at furthering our understanding of the dynamic processes of the Earth/Ocean/Atmosphere system. Our research spans across land and oceans as we seek to understand connections between the continents and oceans, ice-sheet dynamics and the formation and evolution of the Earth as a whole. We study the structure and evolution of the oceanic crust from its formation at mid-ocean ridges to consumption at subduction zones, coupled with the dynamics of the mantle that drives seafloor spreading. We study a wide range of fluid-mediated processes, including those occurring at hydrothermal vents, at shelf-edge seeps and in subduction zone settings. Included in these processes are links to seismicity, fluxes of chemicals to the ocean and mantle, microbial activity and the subseafloor biosphere. We study the role of oceans both in relation to past climate change and as a driver of present day climate dynamics, and use natural archives like from sediments, corals, and tree rings to understand past climate. We study a wide range of coastal processes including the impacts of climate change and storms on coastal regions.
The Department today consists of about 30 Ph.D. level Scientific Staff and another 16 Technical Staff (many of whom hold Ph.D. degrees). In addition there are about 25 graduate students pursuing their Ph.D. through the WHOI/MIT Joint Program and roughly 8 Postdoctoral Scholars, Fellows and Investigators.
The Scientific and Technical staff carry out research that involves sea-going deployments of instruments built in house; laboratory studies using high precision analytical facilities; and theoretical and computational studies of ocean and climate processes and geodynamics. Examples of the facilities within the department include the National Ocean Sciences Accelerator Mass Spectrometry Facility (NOSAMS) and the Northeast National Ion Microprobe Facility (NENIMF). We now run the national Ocean Bottom Seismograph Instrument Center (OBSIC).
Geology & Geophysics Department
Woods Hole, MA (June 16,2021) — Woods Hole Oceanographic Institution (WHOI) climate modeler Dr. Alan Condron and United States Geological Survey (USGS) research geologist Dr. Jenna Hill have found evidence that massive icebergs from roughly 31,000 years ago drifted more than 5000km (> 3,000 miles) along the eastern United States coast from Northeast Canada all the way to southern Florida. These findings were published today in Nature Communications.
Using high resolution seafloor mapping, radiocarbon dating and a new iceberg model, the team analyzed about 700 iceberg scours (“plow marks” on the seafloor left behind by the bottom parts of icebergs dragging through marine sediment ) from Cape Hatteras, North Carolina to the Florida Keys. The discovery of icebergs in this area opens a door to understanding the interactions between icebergs/glaciers and climate.
“The idea that icebergs can make it to Florida is amazing,” said Condron. “The appearance of scours at such low latitudes is highly unexpected not only because of the exceptionally high melt rates in this region, but also because the scours lie beneath the northward flowing Gulf Stream.”
“We recovered the marine sediment cores from several of these scours, and their ages align with a known period of massive iceberg discharge known as Heinrich Event 3. We also expect that there are younger and older scours features that stem from other discharge events, given that there are hundreds of scours yet to be sampled,” added Hill.
To study how icebergs reached the scour sites, Condron developed a numerical iceberg model that simulates how icebergs drift and melt in the ocean. The model shows that icebergs can only reach the scour sites when massive amounts of glacial meltwater (or glacial outburst floods) are released from Hudson Bay. “These floods create a cold, fast flowing, southward coastal current that carries the icebergs all the way to Florida” says Condron. “The model also produces ‘scouring’ on the seafloor in the same places as the actual scours”
The ocean water temperatures south of Cape Hatteras are about 20-25°C (68-77°F). According to Condron and Hill, for icebergs to reach the subtropical scour locations in this region, they must have drifted against the normal northward direction of flow — the opposite direction to the Gulf Stream. This indicates that the transport of icebergs to the south occurs during large-scale, but brief periods of meltwater discharge.
“What our model suggests is that these icebergs get caught up in the currents created by glacial meltwater, and basically surf their way along the coast. When a large glacial lake dam breaks, and releases huge amounts of fresh water into the ocean, there’s enough water to create these strong coastal currents that basically move the icebergs in the opposite direction to the Gulf Stream, which is no easy task” Condron said.
While this freshwater is eventually transferred northward by the Gulf Stream, mixing with the surrounding ocean would have caused the meltwater to be considerably saltier by the time it reached the most northern parts of the North Atlantic. Those areas are considered critical for controlling how much heat the ocean transports northward to Europe. If these regions become abundant with freshwater, then the amount of heat transported north by the ocean could significantly weaken, increasing the chance that Europe could get much colder.
The routing of meltwater into the subtropics – a location very far south of these regions – implies that the influence of meltwater on global climate is more complex than previously thought, according to Condron and Hill. Understanding the timing and circulation of meltwater and icebergs through the global oceans during glacial periods is crucial for deciphering how past changes in high-latitude freshwater forcing influenced shifts in climate.
“As we are able to make more detailed computer models, we can actually get more accurate features of how the ocean actually circulates, how the currents move, how they peel off and how they spin around. That actually makes a big difference in terms of how that freshwater is circulated and how it can actually impact climate,” Hill added.
- The discovery of icebergs in this area opens a door to understanding the interactions between icebergs/glaciers and climate.
- Evidence suggests that there may be hundreds of undiscovered scours that range in ages
- A newly developed iceberg computer model helped the researchers understand the timing and circulation of meltwater and icebergs through the global oceans during glacial periods, which is crucial for deciphering how past changes in high-latitude freshwater forcing influenced shifts in climate.
Woods Hole, Mass. (May 27, 2021) – With the expansion of oxygen-depleted waters in the oceans due to climate change, some species of foraminifera (forams, a type of protist or single-celled eukaryote) that thrive in those conditions could be big winners, biologically speaking.
A new paper that examines two foram species found that they demonstrated great metabolic versatility to flourish in hypoxic and anoxic sediments where there is little or no dissolved oxygen, inferring that the forams’ contribution to the marine ecosystem will increase with the expansion of oxygen-depleted habitats.
In addition, the paper found that the multiple metabolic strategies that these forams exhibit to adapt to low and no oxygen conditions are changing the classical view about the evolution and diversity of eukaryotes. That classical view hypothesizes that the rise of oxygen in Earth’s system led to the acquisition of oxygen-respiring mitochondria, the part of a cell that generates most of the chemical energy that powers a cell’s biochemical reactions. The forams in the study represent “typical” mitochondrial-bearing eukaryotes. However, these two forams respire nitrate and produce energy in the absence of oxygen, with one colonizing an anoxic environment, often with high levels of hydrogen sulfide, a chemical compound typically toxic to eukaryotes.
“Benthic foraminifera represent truly successful microbial eukaryotes with diverse and sophisticated metabolic adaptive strategies” that scientists are just beginning to discover, the authors noted in the paper, Multiple integrated metabolic strategies allow foraminiferal protists to thrive in anoxic marine sediments appearing in Science Advances.
This is important because scientists have studied forams extensively for interpreting past oceanographic and climate conditions. Scientists largely have assumed that forams evolved after oxygen was on the planet and likely require oxygen to survive. However, finding that forams can perform the processes described “throws a whole new wrench in interpretations of past environmental conditions on Earth, driven by the foram fossil record,” said co-author and project leader Joan Bernhard, senior scientist in the Geology and Geophysics Department at the Woods Hole Oceanographic Institution (WHOI).
Bernhard said that over the past several decades she has worked to establish that forams can live where there is little or no oxygen. “We never knew exactly why forams can live where there isn’t any oxygen until molecular methods got good enough that we could really start to ask some of these questions. This is our first paper that’s coming out with some of these insights,” she said. Bernhard added that with thousands of foram species living today, and with hundreds of thousands extinct, it is likely that this is “the tip of the iceberg” in terms of possibly discovering other metabolic strategies invoked by these forams.
Specific insights from the paper pertain to two highly successful benthic foraminiferal species that inhabit hypoxic or anoxic sediments in the Santa Barbara Basin, a sort of natural laboratory off the coast of California for studying the impact of oxygen depletion in the ocean.
Through gene expression analysis of the two species—Nonionella stella and Bolivina argentea—scientists found different successful metabolic adaptations that allowed the forams to succeed in oxygen-depleted marine sediments and identified candidate genes involved in anaerobic respiration and energy metabolism.
The N. stella is a sort of kleptomaniac, utilizing a technique to steal chloroplasts—the structure in a cell where photosynthesis occurs—from a particular diatom genus. What makes this particularly interesting is that N. stella lives well below what is considered to be the zone where photosynthesis can happen. The authors noted that there has been discussion in the literature questioning the functionality of these kleptoplasts in the Santa Barbara Basin N. stella but the new results show that these kleptoplasts are firmly functional, although exact metabolic details remain elusive.
In addition, the scientists found that the two foram species in the study use different metabolic pathways to incorporate ammonium into organic nitrogen in the form of glutamate, a metabolic strategy that was not previously known to be performed by these organisms.
“The metabolic variety suggests that at least some species of this diverse protistan group will withstand severe deoxygenation and likely play major roles in oceans affected by climate change,” the authors wrote.
The study “gives the scientific community a new direction for research,” said lead author Fatma Gomaa, who, at the time of the study, was a postdoctoral investigator at the Geology and Geophysics Department at WHOI. “We are now starting to learn that there are microeukaryotes living in habitats similar to those in Earth’s early history that are performing very interesting biological functions. Learning about these forams is very intriguing and will shed light on how early eukaryotes evolved.”
About Woods Hole Oceanographic Institution
The Woods Hole Oceanographic Institution (WHOI) is a private, non-profit organization on Cape Cod, Massachusetts, dedicated to marine research, engineering, and higher education. Established in 1930, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate an understanding of the ocean’s role in the changing global environment. WHOI’s pioneering discoveries stem from an ideal combination of science and engineering—one that has made it one of the most trusted and technically advanced leaders in basic and applied ocean research and exploration anywhere. WHOI is known for its multidisciplinary approach, superior ship operations, and unparalleled deep-sea robotics capabilities. We play a leading role in ocean observation and operate the most extensive suite of data-gathering platforms in the world. Top scientists, engineers, and students collaborate on more than 800 concurrent projects worldwide—both above and below the waves—pushing the boundaries of knowledge and possibility. For more information, please visit www.whoi.edu
Authors: Fatma Gomaa1,2*, Daniel R. Utter2, Christopher Powers3, David J. Beaudoin1, Virginia P. Edgcomb1, Helena L. Filipsson4, Colleen M. Hansel5, Scott D. Wankel5, Ying Zhang3, and Joan M. Bernhard1*
1Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
2Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
3Department of Cell and Molecular Biology, College of the Environment and Life Sciences, University of Rhode Island, Kingston, RI, USA
4Lund University, Department of Geology, Lund, Sweden.
5Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA