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 – Greenland may be best known for its enormous continental scale ice sheet that soars up to 3,000 meters above sea level, whose rapid melting is a leading contributor to global sea level rise. But surrounding this massive ice sheet, which covers 79% of the world’s largest island, is Greenland’s rugged coastline dotted with ice capped mountainous peaks. These peripheral glaciers and ice caps are now also undergoing severe melting due to anthropogenic (human-caused) warming. However, climate warming and the loss of these ice caps may not have always gone hand-in-hand.
New collaborative research from the Woods Hole Oceanographic Institution and five partner institutions (University of Arizona, University of Washington, Pennsylvania State University, Desert Research Institute and University of Bergen), published today in Nature Geoscience, reveals that during past periods glaciers and ice caps in coastal west Greenland experienced climate conditions much different than the interior of Greenland. Over the past 2,000 years, these ice caps endured periods of warming during which they grew larger rather than shrinking.
This novel study breaks down the climate history displayed in a core taken from an ice cap off Greenland’s western coast. According to the study’s researchers, while ice core drilling has been ongoing in Greenland since the mid-20th century, coastal ice core studies remain extremely limited, and these new findings are providing a new perspective on climate change compared to what scientists previously understood by using ice cores from the interior portions of the Greenland ice sheet alone.
“Glaciers and ice caps are unique high-resolution repositories of Earth’s climate history, and ice core analysis allows scientists to examine how environmental changes – like shifts in precipitation patterns and global warming – affect rates of snowfall, melting, and in turn influence ice cap growth and retreat,” said Sarah Das, Associate Scientist of Geology and Geophysics at WHOI. “Looking at differences in climate change recorded across several ice core records allows us to compare and contrast the climate history and ice response across different regions of the Arctic.” However, during the course of this study, it also became clear that many of these coastal ice caps are now melting so substantially that these incredible archives are in great peril of disappearing forever.
Due to the challenging nature of studying and accessing these ice caps, this team was the first to do such work, centering their study, which began in 2015, around a core collected from the Nuussuaq Peninsula in Greenland. This single core offers insight into how coastal climate conditions and ice cap changes covaried during the last 2,000 years, due to tracked changes in its chemical composition and the amount of snowfall archived year after year in the core. Through their analysis, investigators found that during periods of past warming, ice caps were growing rather than melting, contradicting what we see in the present day.
“Currently, we know Greenland’s ice caps are melting due to warming, further contributing to sea level rise. But, we have yet to explore how these ice caps have changed in the past due to changes in climate,” said Matthew Osman, postdoctoral research associate at the University of Arizona and a 2019 graduate of the MIT-WHOI Joint program. “The findings of this study were a surprise because we see that there is an ongoing shift in the fundamental response of these ice caps to climate: today, they’re disappearing, but in the past, within small degrees of warming, they actually tended to grow.”
According to Das and Osman, this phenomenon happens because of a “tug-of-war” between what causes an ice cap to grow (increased precipitation) or recede (increased melting) during periods of warming. Today, scientists observe melting rates that are outpacing the rate of annual snowfall atop ice caps. However, in past centuries these ice caps would expand due to increased levels of precipitation brought about by warmer temperatures. The difference between the past and present is the severity of modern anthropogenic warming.
The team gathered this data by drilling through an ice cap on top of one of the higher peaks of the Nuussuaq Peninsula. The entire core, about 140 meters in length, took about a week to retrieve. They then brought the meter-long pieces of core to the National Science Foundation Ice Core Facility in Denver, Colorado, and stored at -20 degrees Celsius. The core pieces were then analyzed by their layers for melt features and trace chemistry at the Desert Research Institute in Reno, Nevada. By looking at different properties of the core’s chemical content, such as parts per billion of lead and sulfur, investigators were able to accurately date the core by combining these measurements with a model of past glacier flow.
“These model estimates of ice cap flow, coupled with the actual ages that we have from this high precision chemistry, help us outline changes in ice cap growth over time. This method provides a new way of understanding past ice cap changes and how that is correlated with climate,” said Das. “Because we’re collecting a climate record from the coast, we’re able to document for the first time that there were these large shifts in temperature, snowfall and melt over the last 2,000 years, showing much more variability than is observed in records from the interior of Greenland,” Das added.
“Our findings should urge researchers to return to these remaining ice caps and collect new climate records while they still exist,” added Osman.
Additional collaborators and institutions:
Benjamin Smith, University of Washington
Luke Trusel, Pennsylvania State University
Joseph McConnell, Desert Research Institute
Nathan Chellman, Desert Research Institute
Monica Arienzo, Desert Research Institute
Harald Sodemann, University of Bergen and Bjerknes Centre for Climate Research, Norway
This research is funded by the National Science Foundation (NSF), with further support from the U.S. Department of Defense National Defense Science and Engineering Graduate Fellowship; and an Ocean Outlook Fellowship to the Bjerknes Centre for Climate Research; the National Infrastructure for High Performance Computing and Data Storage in Norway; Norwegian Research Council; and Air Greenland.
Woods Hole, Mass. – A team led by Anne Cohen, a scientist at Woods Hole Oceanographic Institution, received $1.75M in funding from the National Science Foundation (NSF) to study how coral reefs survive extreme heat events caused by climate change. The multidisciplinary project taps into expertise across four WHOI departments to uncover the oceanographic and biological processes that enable corals to survive marine heatwaves.
Coral reefs provide habitat for a quarter of all known marine species and support the livelihoods of a billion people worldwide. But coral reefs everywhere are dying at an alarming rate. Climate change is warming the oceans and as a consequence, marine heatwaves have increased in frequency and intensity. Water temperatures just 1 degree Celsius above normal can cause corals to bleach, but recent heatwaves have far exceeded that threshold in many areas. Indeed, in just the last 4 decades, millions of corals have died, and entire coral reefs have been extinguished due to ocean warming.
The Phoenix Islands Marine Protected Area (PIPA), an oceanic wilderness in the remote tropical Pacific, was established by the island nation of Kiribati in 2006 to protect over 408,000 km2 of ocean habitat, including coral reefs, seamounts and terrestrial ecosystems. Here, in the bullseye of the strongest marine heatwaves, PIPA’s reefs have an inspiring story to tell of adaptation and resilience. According to Cohen and her fellow investigators, many of PIPAs corals succumbed to intense bouts of heat that hit the region in 2002, 2009 and again in 2015. But their data shows some reef areas, each spread across thousands of square meters and hosting a diversity of coral species, did survive and likely played a critical role in the recovery of PIPA’s corals.
“Coral reefs are beautiful, magical places, but they are also incredibly important to humanity. Even in the United States, our coral reefs provide hundreds of thousands of jobs and protect strategic military infrastructure. But now, coral reefs are in crisis because of climate change. The sense of urgency is so great that scientists, conservation organizations and governments of coral reef nations are pulling together to try tackle it, and WHOI is playing a vital role,” said Cohen.
Cohen and WHOI scientists Michael Fox, Weifeng (Gordon) Zhang, Simon Thorrold, Steven Lentz, and Nathaniel Mollica, and MIT-WHOI graduate student, Phadtaya ‘Pad’ Poemnamthip will test the hypothesis that coral resilience to extreme heat is ultimately rooted in the dynamic reef environment. Combining sensors deployed on the reefs with sophisticated hydrodynamic models, they show that water temperature and flow in and around coral reefs is highly variable over small spatial scales and dramatically different from that of the open ocean that surrounds them. This fine-scale mosaic of environmental conditions sets the stage for coral survival in two main ways. In areas on the reef where waters are naturally and chronically warmer than the open ocean, corals have the opportunity to genetically adapt to higher temperatures. Conversely, in other areas on the reef where cool water may be episodically upwelling from the deep, corals are able to shelter from the heat.
“This achievement was possible because of WHOI’s long-term commitment to the PIPA, not only doing world-class science, but building relationships with Kiribati, learning from the Kiribati people, collaborating, training and sharing our findings” Cohen said. “It’s not just about collecting data and zipping back to the lab. What WHOI does in the world matters. People matter.”
While Kiribati observers have joined all prior expeditions to the PIPA, this award explicitly supports the participation and training of Kiribati residents and high school students. “Thanks to WHOI for its tireless efforts and support for the corals in the PIPA, and we’re equally thrilled about the involvement of Kiribati students and the Kanton residents in upcoming projects. This is an important step for building local capacity in these specialized areas of marine science,” said Teburoro Tito, Kiribati Ambassador to the United States, Permanent Representative to the United Nations and Chair of the PIPA Trust Board.
The WHOI team will lead two expeditions to the PIPA, sailing thousands of miles across the remote central Pacific aboard the 72-ft sailboat Seadragon, operated by the non-profit Pangaea Explorations. Combining high resolution 3-D hydrodynamic models, oceanographic observations, physiological assays, coral chemistry, and skeletal records of growth and bleaching, they will study the processes that enable PIPA’s corals to survive extreme heat. This new knowledge will help scientists and coral reef managers everywhere to determine where in the world climate resilient corals exist, predict their chances of survival as the global ocean continues to warm, and identify the strongest corals for conservation and reef restoration.
Researchers Emphasize the Need for Baseline Information of Microbial Food Webs
The hydrothermal vent fluids from the Gorda Ridge spreading center in the northeast Pacific Ocean create a biological hub of activity in the deep sea. There, in the dark ocean, a unique food web thrives not on photosynthesis but rather on chemical energy from the venting fluids. Among the creatures having a field day feasting at the Gorda Ridge vents is a diverse assortment of microbial eukaryotes, or protists, that graze on chemosynthetic bacteria and archaea.
This protistan grazing, which is a key mechanism for carbon transport and recycling in microbial food webs, exerts a higher predation pressure at hydrothermal vent sites than in the surrounding deep-sea environment, a new paper finds.
“Our findings provide a first estimate of protistan grazing pressure within hydrothermal vent food webs, highlighting the important role that diverse deep-sea protistan communities play in deep-sea carbon cycling,” according to the paper, Protistan grazing impacts microbial communities and carbon cycling ad deep-sea hydrothermal vents published in the Proceedings of the National Academy of Sciences (PNAS).
Protists serve as a link between primary producers and higher trophic levels, and their grazing is a key mechanism for carbon transport and recycling in microbial food webs, the paper states.
The research found that protists consume 28-62% of the daily stock of bacteria and archaea biomass within discharging hydrothermal vent fluids from the Gorda Ridge, which is located about 200 kilometers off the coast of southern Oregon. In addition, researchers estimate that protistan grazing could account for consuming or transferring up to 22% or carbon that is fixed by the chemosynthetic population in the discharging vent fluids. Though the fate of all of that carbon is unclear, “protistan grazing will release a portion of the organic carbon into the microbial loop as a result of excretion, egestion, and sloppy feeding,” and some of the carbon will be taken up by larger organisms that consume protistan cells, the paper states.
After collecting vent fluid samples from the Sea Cliff and Apollo hydrothermal vent fields in the Gorda Ridge, researchers conducted grazing experiments, which presented some technical challenges that needed to be overcome. For instance, “prepping a quality meal for these protists is very difficult,” said lead author Sarah Hu, a postdoctoral investigator in the Marine Chemistry and Geochemistry Department at the Woods Hole Oceanographic Institution (WHOI).
“Being able to do this research at a deep-sea vent site was really exciting because the food web there is so fascinating, and it’s powered by what’s happening at this discharging vent fluid,” said Hu, who was onboard the E/V Nautilus during the May-June 2019 cruise. “There is this whole microbial system and community that’s operating there below the euphotic zone outside of the reach of sunlight. I was excited to expand what we know about the microbial communities at these vents.”
Hu and co-author Julie Huber said that quantitative measurements are important to understand how food webs operate at pristine and undisturbed vent sites.
“The ocean provides us with a number of ecosystem services that many people are familiar with, such as seafood and carbon sinks. Yet, when we think about microbial ecosystem services, especially in the deep sea, we just don’t have that much data about how those food webs work,” said Huber, associate scientist in WHOI’s Marine Chemistry and Geochemistry Department.
Obtaining baseline measurements “is increasingly important as these habitats are being looked at for deep-sea mining or carbon sequestration. How might that impact how much carbon is produced, exported, or recycled?” she said.
“We need to understand these habitats and the ecosystems they support,” Huber said. “This research is connecting some new dots that we weren’t able to connect before.”
The research was supported by NASA, the National Oceanic and Atmospheric Administration, Ocean Exploration Trust, the National Science Foundation, and WHOI.
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
Sarah K. Hu1*, Erica L. Herrera1, Amy R. Smith1, Maria G. Pachiadaki2, Virginia P. Edgcomb3, Sean P. Sylva1, Eric W. Chan4, Jeffrey S. Seewald1, Christopher R. German3, and Julie A. Huber1
1 Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
2 Department of Biology, Woods Hole Oceanographic Institution, Woods Hole MA, USA
3 Department of Geology & Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
4 School of Earth, Environment & Marine Sciences, UT-RGV, Edinburg, TX, USA