A team of international scientists known as the NICOPP (Nitrogen Cycle in the Ocean, Past and Present) working group, led by Dalhousie oceanographer Markus Kienast and Eric Galbraith of McGill University, use these cylinders to measure isotopes of nitrogen on the seafloor that arise from nitrogen-rich phytoplankton sinking and collecting in the mud.
“Over thousands of years, this slow accumulation builds up a vertical record of past changes that can be sampled by taking a sediment core using a specialized ship,” says Dr. Kienast. “As you go down in the core, you go back in time.”
In a new paper, published last week in Nature Geoscience, the NICOPP working group presented the first global synopsis of available sedimentary nitrogen isotope records from throughout the world’s oceans, spanning the past 30,000 years.
“The results confirm the ocean is an effective self-regulator with respect to nitrogen, a major nutrient,” says Dr. Kienast, “but reaching equilibrium after a disturbance such as the last glacial-interglacial warming can take hundreds or thousands of years.”
That’s a concern, given the scale and speed of current anthropogenic changes. In recent years, human activity, rather than natural causes, has become the main factor in oceanic change around the world. Global warming, along with the heavy use of nitrogen-based fertilizers for agriculture, is pushing the natural ocean nitrogen cycle off balance.
“Despite its importance for all marine life, we don’t really have a good handle on how the global ocean will react to these changes,” said Dr. Galbraith. “With too little nitrogen, the ecosystem would starve. Too much, and the decay of sinking phytoplankton would use up the oxygen dissolved in ocean water, suffocating fish and other marine animals.”
This highlights the importance of research on the interplay between climate change and ocean biogeochemistry.
Previous studies on nitrogen isotopes in marine sediment records had shown signs of changes in denitrification at the end of the ice age, in some localized places. But the nitrogen isotope records are difficult to interpret from individual sites alone.
“Our research was driven by our need to provide quantitative constraints of climate change effects on the global ocean,” says Dr. Kienast.
After three years of research, the international team, composed of 35 ocean researchers, completed their goal of assembling a global network of sediment records to see the full picture clearly and compare the results with computer models of the ocean.
“This publication is not the end of it,” says Dr. Kienast. “We have a great group of enthusiastic scientists and we are looking to broaden our group and expand our research. Stay tuned.”
On his recent trip collecting sediment samples in the western tropical Pacific, Dr. Kienast was accompanied by Dalhousie MSc student Liz Kerrigan.
“If you like getting muddy, then you’ll love sediment work,” says Kerrigan. “Ultimately, this information from the sediment helps us reveal a little bit more about what’s happening in the ocean, both today and in the past”.
It is not a rare occasion for Dalhousie Oceanography graduate students to spend time at sea — it’s a key program requirement.
“A requirement that they are usually more than happy to fulfill,” says Dr. Kienast.
Regis Dudley, Communications, Faculty of Science, Dalhousie University, (902) 494-4105, email@example.com
Regis Dudley | Newswise
NASA sees heavy rain in Tropical Cyclone Chan-Hom
02.07.2015 | NASA/Goddard Space Flight Center
Creating a stopwatch for volcanic eruptions
02.07.2015 | Arizona State University
Wind turbines could be installed under some of the biggest bridges on the road network to produce electricity. So it is confirmed by calculations carried out by a European researchers team, that have taken a viaduct in the Canary Islands as a reference. This concept could be applied in heavily built-up territories or natural areas with new constructions limitations.
The Juncal Viaduct, in Gran Canaria, has served as a reference for Spanish and British researchers to verify that the wind blowing between the pillars on this...
New technique combines electron microscopy and synchrotron X-rays to track chemical reactions under real operating conditions
A new technique pioneered at the U.S. Department of Energy's Brookhaven National Laboratory reveals atomic-scale changes during catalytic reactions in real...
Think of an object made of iron: An I-beam, a car frame, a nail. Now imagine that half of the iron in that object owes its existence to bacteria living two and a half billion years ago.
Think of an object made of iron: An I-beam, a car frame, a nail. Now imagine that half of the iron in that object owes its existence to bacteria living two and...
A team of scientists including PhD student Friedrich Schuler from the Laboratory of MEMS Applications at the Department of Microsystems Engineering (IMTEK) of...
The three-year clinical trial results of the retinal implant popularly known as the "bionic eye," have proven the long-term efficacy, safety and reliability of...
25.06.2015 | Event News
16.06.2015 | Event News
11.06.2015 | Event News
03.07.2015 | Press release
03.07.2015 | Agricultural and Forestry Science
03.07.2015 | Health and Medicine