Monday, May 16, 2011

The Water Chemist

Leverett Glacier comes off of the Greenland Ice Sheet from the east. The main portal, which funnels meltwater from most of the glacier’s catchment area, discharges a river on the north side of the glacier. Our camp is just north of this river sitting on top of a saddle between two small peaks. Before yesterday, only a few people from our camp had ever ventured to the south side of the river or explored the rest of the glacier’s terminus. In the early season, we’ve assumed the river ice was too dangerous to cross and in the summer high flows make crossing impossible. However, this year has been unseasonably cold and in places, the river ice is still almost two feet thick. Yesterday, Jemma Wadham, Matt Charette and I walked across the frozen river to search for new field sites. We carried packs full of equipment to assist in our assessments and interpretations.
Home away from home.

Huge piles of rocks and dirt sit in front of Leverett Glacier as if a massive bulldozer had pushed them there and then left. In front of these piles, the landscape might as well be the Moon’s surface. No trees, grasses or even weeds take root here, and so there is nothing but mud, sand, rocks and ice. The only sign of life we saw was the occasional fox and geese tracks. As we hiked, we discovered several small ponds and a stream feeding back to the main river. There were also several springs of groundwater coming up through the rocks. One was obviously different. It was trickling out of the top of a 30-foot mound of ice and was blood red. To figure out what it was, we deployed our arsenal of water chemistry tools.

The first thing we checked was the electrical conductivity of the water. We do this to measure the amount of ions in the water. Ions are dissolved free elements or small combinations of elements floating freely through the water. Ions are either negatively or positively charged. For example, if you add table salt to a glass of water, you are adding sodium chloride salt (NaCl) that dissolves to Na+ and Cl-. Sodium has a +1 charge while chloride has a -1 charge and so no matter how much table salt you add to water, the total charge remains neutral but the conductivity of the water will increase. In fact, one of the most important laws of water chemistry is that all waters have an equal amount of negative and positive ions. Basically, our electrical conductivity meter measures the amount of salt dissolved in the water. For our purposes, a low conductivity measurement likely indicates recent snowmelt, whereas a high reading means the water is likely older and has traveled a long distance. Older water has spent more time weathering rocks and so contains more dissolved ions. We are most interested in water that has spent time under the glacier as it might tell us about the glacier itself. We assume that this "basal water" (water from the glacier's base)  will have a significantly higher conductivity than recent snowmelt. The blood red ice spring had exceptionally high conductivity so we knew its water source was distant.

Chemistry with a view.
Next, we checked the pH. pH is the “master” variable for water chemistry and is the most important parameter for most chemical studies. Using only a simple hand held pH probe, a decent chemist can map out the extent of an oil spill, determine the source of groundwater, or even make guesses as to what rocks the water has been in contact with. Are plants photosynthesizing in the water? Check the pH. Can your drinking water carry dissolved uranium? Check the pH. In our case, we use pH for the same reason we use conductivity. That is to try to differentiate between recent snowmelt and water from the bottom of the glacier. Snowfall should be in equilibrium with carbon dioxide, an acid, and so should have a lower pH than water coming from under the glacier. Our blood red springs has a pH of 8, meaning the water is more alkaline and is certainly not recent snowmelt.

After taking a pH reading, we collected water to analyze back at our university labs. We fill multiple bottles of various sizes, each for a specific purpose. Some of these samples are filtered before they are collected while others are taken raw. How each bottle is filled is also important. For dissolved gas samples we fill and cap the bottle underwater to ensure there are no bubbles to lose gas through. In contrast, a head space is left at the top of each dissolved metal bottle as those bottles will be frozen and we don’t want them to burst. The things we can’t measure in the field include oxygen and deuterium isotopes, dissolved organic carbon, fatty lipids, anions, cations, metals, and alkalinity. Each of these parameters requires special equipment, trained technicians, and each analysis needs to be completed within a specified amount of time. The data will be used to build models, fuel interpretations, give talks, and publish papers.

At each site, I take as many notes as time allows. Each entry is dated and the time is recorded, and each stop is given a unique name (something like GRE-11-009). I also use a hand held global positioning unit (GPS) to record each location. In addition to recording all the parameters measured on site, I make sketches of the glacier and possible water flow paths. I also write down any interpretations made at each site. Phil Bennet, my master’s degree advisor would always tell me, “Interpret as you go!” and so I do. In the old days scientists would spend a great deal of time crafting their field notes, making detailed drawings and writing extensive interpretations. Today, I think some of this art is lost though most college level field courses grade heavily on a student’s field notes.

Finally, we take pictures of each field site and use notebooks, pencils and each other for scale. These pictures will wind up being projected on large screens at meetings when we present our findings and ideally, the pictures won’t show us with dumb looks on our faces.

Red water. Why? Photo by Matt Charette
Last year, some German geologists stopped by camp and described the blood red spring to the team. To explain the color, they invoked a plane crash to account for the amount of iron that was obviously staining everything. In science, this is what is know as “arm waving,” which is basically coming up with far fetched ideas to explain something while likely waving your arms for emphasis. When I first saw the springs, I noticed the deep black clay we were walking through near the spring and the dark black metamorphic rocks surrounding it. Without really knowing what I was talking about, I suggested an iron ore body below us. Again, more arm waving. Matt and Jemma came to a more logical conclusion.

Long ago, before Leverett Glacier existed, this area of Greenland was covered in trees and grasses. Then, over a long period of time, Leverett Glacier formed off of the Greenland Ice Sheet and bulldozed over all the vegetation covering it under layers and layers of ice. This ancient forest is still here except that now it is in the form of simple dissolved organic carbon. Today this carbon is food for an array of bacteria that have been slowly munching away on it ever since it was buried by the glacier. When these bugs eat carbon they need to dispose of the carbon’s electrons and so they give the electrons to oxygen. This is exactly what we do every time we take a breath. Under the glacier with no new source of oxygen, these oxygen-breathing bugs quickly used all the oxygen and died out. This made way for a new breed of bugs. These new bugs were breathing iron, pulling it out of the rocks to dispose of the electrons taken from carbon. When bacteria do this, the iron no longer wants to form minerals and becomes dissolved in the water. Today, the water flowing under Leverett Glacier is full of the used iron bugs have breathed, and when this iron reaches the surface at our blood red springs, it meets again with oxygen and forms a microcrystalline red mineral, rust, over everything the water touches. If there is one truth about life on Earth it is that if life can exist, it will. Even if it is under a glacier without any oxygen.

Jemma Wadham, the principle investigator of our team, is a professor of physical geography in the Bristol Glaciology Center at the University of Bristol, and Matt Charette, my advisor, is a scientist in the Department of Marine Chemistry and Geochemistry at the Woods Hole Oceanographic Institution.


  1. Love the explanation! Wish I'd gone to see that part of the other side of the river. Are you loving the Musk-ox burgers?

  2. Mr. Linhoff, careful with what you say about the German people. I think a plane crash is a very smart explanation of the color... :)