Using Time as Our Guide

By Bianca Greeff, Graduate Assistant.

Both urban and rural areas around the world rely heavily on groundwater to support agriculture, energy, residential, and industrial use. This demand for groundwater—from a global population of over seven and a half billion—combined with impacts of climate change places more stress on these systems. In order to sustainably manage these resources, we first need to quantify it.

Kip Solomon, department of Geology & Geophysics at the University of Utah, will show how understanding the age and recharge of aquifers can lead to more sustainable use at the GCSC Seminar Series on Tuesday, Jan. 23, 4-5 p.m. in 210 ASB.

“While we have a hint that we are overexploiting a number of these large regional systems,” said Solomon, “the amount of data we have to make these assessments is rather limited. Part of my pitch is that we need to make more measurements in these kinds of systems.”

Groundwater recharge is a hydrologic process where water moves from surface water to groundwater—like an aquifer—by draining through the soil. Recharge can be a slow process, especially when the body of water is deep underground. The longer it takes water to reach the aquifer, the lower the rate of recharge. This makes measuring the rate of recharge a challenging process. For Solomon, the most promising tool is dating the groundwater.

“By getting the mean age of water we can calculate the recharge,” explained Solomon. “By dating the groundwater and using the geologic information to determine the volume, we can infer the rates of replenishment to the aquifer.”

There are a few tools that can be used to date water—namely isotopes and trace atmospheric gasses. Elements can have several isotopes depending on what the element has come in contact with. In aquifers, isotopes are often generated in the subsurface. Their concentrations build up the longer the water is in contact with the subsurface rock. A higher concentration of an isotope, like Carbon-14, thus signifies older water.

For younger water, atmospheric gasses can be used to date it. Over the past few decades, gasses produced in the industrial processes—like sulfur hexafluoride—have been increasing. When exposed to the air, water absorbs concentrations of these gasses. The longer the water interacted with the gas, the greater the concentration will be. Once the water moves below the surface those concentrations of gas are essentially “locked in.” Measuring the traces of these gasses in groundwater can show how old that water might be.

Determining the recharge rate is important for both hydrologic understanding of subsurface bodies of water and for natural resource management. The recharge is a vital component of understanding the amount of water that can be extracted without overexploiting or compromising the integrity of the groundwater body.

“99 percent of unfrozen freshwater is in the ground,” explained Solomon. “As our world approaches eight billion, it is a growing question of whether or not these big regional aquifers can be sustainably exploited to support agriculture in arid and semi-arid regions.”

To learn more, attend Solomon’s lecture, “Can Groundwater Feed the World? It’s All About Time” on Tuesday, Jan. 23 at 4 p.m. in 210 ASB.

 

Cover photo via USGS public domain. 

INVESTIGATING CONTAMINATION

Bianca Greeff, Graduate Assistant

The Marcellus shale in northeastern Pennsylvania is estimated to hold up to 500 trillion cubic feet of natural gas, possibly making it the second largest natural gas field in the world. The deep sedimentary rock of the Marcellus requires hydraulic fracturing to access the natural gas trapped between rock layers.

By John G. Van Hoesen [CC BY-SA 4.0], via Wikimedia Commons

Hydraulic fracturing (fracking) is when a chemical mixture is pumped into the subsurface at high pressures to fracture the rock and release gas used for energy production. Fracturing operations may have the potential to contaminate surface and drinking water, but finding the source of the polluting contaminants is a controversial undertaking. Scientists have relied on isotopes to assess contaminant sources.

Jennifer C. McIntosh, a University Distinguished Scholar and Associate Professor in the Department of Hydrology & Atmospheric Sciences at the University of Arizona, will critically evaluate how tracing isotopes can help identify contaminants from hydraulic fracturing at the GCSC Seminar Series on Tuesday, April 18 from 4-5 p.m. in 210 ASB.

Almost every element comes in multiple forms. Each element contains a characteristic number of protons—as that is what allows the atom to be identified. The number of neutrons for that element can vary. Atoms with the same number of protons and electrons but different numbers of neutrons are isotopes.

Isotopes have been used to track sources of contamination (like brine, fracking fluids, methane, or natural gas) to see if the contaminant is natural or human created. McIntosh describes isotopes as a fingerprint. Tracing these fingerprints is an effective way to identify where a contaminant is coming from.

“Depending on what geology an element or water interacts with,” McIntosh said, “the element is going to pick up a particular signature. This is a forensics type of work, you are essentially an investigator.”

By Joshua Doubek (Own work) [CC BY-SA 3.0], via Wikimedia Commons

McIntosh will point to contamination case studies from the Marcellus Shale gas production, and the Bakken Shale oil production in North Dakota. She will also talk about her own work collecting baseline studies on methane and shallow aquifers in Ontario, Canada. In case there are future environmental impacts—like leakage of natural gas or fracturing fluids—from future hydraulic fracturing in the area, McIntosh’s data will serve as a baseline of what Ontario was like before contamination

“Ontario has a shale that is equivalent to the Marcellus Shale, but there has been no shale gas production” explained McIntosh.

Using her expertise in natural tracers, McIntosh developed a road map agencies can use to determine if there is any contamination from oil and gas production. In it, McIntosh illuminates what an agency would want to do beforehand to have the best baseline data in place, the data they would want to collect during a fracking operation, and what data to collect afterward if contamination is suspected.

Learn more at McIntosh’s lecture, “Tracing Environmental Impacts of Hydraulic Fracturing and Oil/Gas Production” on Tuesday, April 18 at 4 pm in 210 ASB.

Cover Photo: By lalabell68 [CC0 Public Domain], via Pixabay

SEMINAR: GREENLAND ICE SHEET MAY HAVE LARGER THAN EXPECTED IMPACT ON SEA LEVEL

By: Liz Ivkovich, Sustainability Office.

New research suggests that the Greenland Ice Sheet is far less stable than current climate models predict, which could mean those models are severely underestimating potential sea level rise.

The ice sheet contains the equivalent of 24 feet of global sea level rise if it melts.

Joerg Schaefer, a paleoclimatologist at Columbia University’s Lamont-Doherty Earth Observatory, will present this new finding and why it matters at the GCSC Seminar Series on Jan. 17 from 4–5 p.m. in 210 ASB.

The Greenland Ice Sheet (GIS) is part of Earth’s cryosphere, the frozen water component of our climate system. The cryosphere plays a vital role in regulating planet temperature, sea levels, currents, and storm patterns. Over Earth’s billions of years, elements of the cryosphere have melted and re-frozen. Understanding how these elements have acted in geologic time scales and during prior periods of climate change enables scientists to model how Earth’s systems will react as the climate warms in the future.

Current climate models, including those developed by the Intergovernmental Panel on Climate Change, are based on the assumption that Greenland’s ice sheet had been relatively stable over the past several million years. The stability of the GIS is under debate. If the GIS was frozen in the past when natural ‘forcing’ (causes) warmed the globe, that means it could stay stable despite human-caused global warming. Unfortunately, Schaefer’s research finds direct evidence from bedrock underneath the ice that the GIS is more at risk of melting than scientists expected.

“We came up with the worrisome result that the Greenland Ice Sheet was actually rather dynamic under natural forcing, which basically immediately means our models overestimate stability with respect to ongoing climate change…” Schaefer explained. “[The prior melting] was due to periods of natural forcing. We will overtake this by anthropogenic forcing very soon, and we just don’t have an argument to expect that the Greenland Ice Sheet will not go again.”

A map of the Greenland Ice Sheet. By Eric Gaba, CC BY-SA 3.0, via Wikimedia Commons

Schaefer and his Lamont-Doherty Earth Observatory Cosmogenic Dating Group’s discovery is the result of groundbreaking direct evidence from rock underneath the ice’s surface. Schaefer said the researchers asked the rock a question: “Have you ever been exposed to open sky?”

The rock Schaefer is referring to is a sample of bedrock from several miles below the ice sheet, obtained in the early 1990s. It took researchers nearly five years to drill out these rocks; the deepest ice core recovered in the world at that time. The sample is so precious that Schaefer and his predecessors didn’t want to work on them until they knew that the research method would produce accurate results. Enter cosmogenic nuclide technique.

Cosmogenic nuclide technique counts the cosmogenic nuclides in the near surface of the rock. These isotopes are produced when extraterrestrial radiation—cosmic rays—trigger a reaction in rock. The reaction produces radioactive beryllium-10 and aluminum-26 isotopes.

“These nuclides are characteristic for cosmic rays, so whenever you measure the nuclides in excess, you know that it’s due to exposure to open sky,” Schaefer explained. “If you measure these nuclides underneath an ice sheet, you know that the ice was gone.”

Schaefer describes these isotopes as sisters that always occur and decay in a specific ratio to each other. Knowing this relationship enables the scientists to count how long the rock was exposed to open sky, and when it was covered again with ice. Though the process is theoretically simple, it is very complicated to measure. It yields an unprecedented direct record of how the ice has melted and refrozen in the past.

The instability of the ice sheet has implications for policy. Translating this, and other climate science research into governance, is what Schaefer calls the “biggest frontier in climate science.”

“Many of the scientific findings are robust and clear, and now the next step is we have to become much better in transferring that into real decisions,” Schaefer said.

Learn more at Schaefer’s lecture, “Ice sheets, glaciers and society: Past and present cryospheric change and its impact on society,” on Jan. 17 at 4 pm in 210 ASB.

Cover Photo: The Greenland Ice Sheet. By Christine Zenino, CC BY 2.0, via Wikimedia Commons.