Please select your home edition
Edition
Naiad

Glaciers contribute essential nutrient to North Atlantic Ocean

by Woods Hole Oceanographic Institution on 14 Mar 2013
Close-up of the outlet of the ‘N’ glacier outflow. The meltwater exiting the base of the glacier is extremely turbid, with high suspended sediment loads from interaction with the bedrock and sediments beneath the glacier Ben Gready, University of Alberta
All living organisms depend on iron as an essential nutrient. In the ocean, iron’s abundance or scarcity means all the difference as it fuels the growth of plankton, the base of the ocean’s food web.

A new study by biogeochemists and glaciologists at Woods Hole Oceanographic Institution (WHOI) identifies a unexpectedly large source of iron to the North Atlantic – meltwater from glaciers and ice sheets, which may stimulate plankton growth during spring and summer. This source is likely to increase as melting of the Greenland ice sheet escalates under a warming climate.

The study was published online in Nature Geoscience on March 10, 2013.

'There’s only been one other study looking at the amount of iron that’s being released in meltwater runoff itself,' says Maya Bhatia, a graduate of the MIT/WHOI Joint Program in Oceanography and Applied Ocean Sciences and Engineering, and the study’s lead author, 'and that had reported high nanomolar concentrations. So to find iron in concentrations several orders of magnitude higher – in the micromolar range – was very surprising.'

Iron from wind-blown dust and river runoff fuels annual plankton blooms in the world’s ocean. Ice sheets and glaciers are now also thought to contribute iron from sediments on the bottom of calved icebergs and glacially-derived dust. Until now, meltwater runoff from glaciers and ice sheets was considered too dilute to carry much iron, although previous research has shown a strong correlation between the plankton blooms and the runoff from Greenland ice sheet.

'Glacial runoff has only recently been considered a potentially important source of nutrients that are useable, or bioavailable, to downstream ecosystems,' says Bhatia. 'We believe our study now adds iron to that list of nutrients, and underscores the potential for a unique but as-yet-undetermined chemical impact from increasing ice sheet meltwater runoff.'

During the course of two expeditions to the Greenland ice sheet in May and July 2008, Bhatia and her colleagues collected samples from sites at several land-terminating glaciers on the western side of the Greenland ice sheet. The glaciers’ meltwater empties into a large lake, which eventually drains into an estuary system before reaching the open ocean. Their study reports levels of dissolved iron orders of magnitude higher than previously found for Greenland glacial runoff rivers. When the WHOI team extrapolated their findings to calculate the contribution of iron from the entire ice sheet, they estimated its value to be within the range of that from dust deposition in the North Atlantic, which is believed to be the primary source of bioavailable iron to this ocean. This value is only an order of magnitude lower than the estimated annual contribution of iron from rivers worldwide.

When an ice sheet or glacier melts, most of the water doesn’t simply run off the surface of the ice sheet. Instead it first drains to the bedrock below the ice sheet through cracks and conduits called moulins and then exits in large runoff rivers.

'A lot of people think of a glacier and an ice sheet as a big block of ice,' says Bhatia, 'but it’s actually quite a porous, complicated system underneath a glacier, with lots of moulins and crevasses leading to the bottom. Once you get into the bottom, there are large tunnels that these waters are passing through.' The more time the water spends in contact with the bedrock and sediments beneath the glacier, the more nutrients it picks up, including iron.

The WHOI team says further research is needed to determine how much of this iron actually reaches the open ocean, as their study followed the meltwater from the edge of the glaciers to the large lake they empty into. For this study, the team assumed that the amount of iron filtered out as the water moves through estuaries before reaching the marine environment would be roughly the same for glacial systems as it is for river systems.

The researchers hope to do more work to confirm the study’s numbers by sampling over a larger geographical area. Additional research could also confirm whether this influx of iron is in a form that can be easily utilized by phytoplankton and therefore stimulates primary production in the ocean.

'We don’t have enough historical measurements to say that this iron contribution is an increase over past conditions, but if it is working the way we think it is, the contribution would be greater as meltwater discharge increases,' Bhatia says. 'It is interesting to think that, as ice sheets melt, there are biogeochemical considerations beyond changing sea level.'

Maya Bhatia is currently a postdoctoral fellow in the Department of Microbiology and Immunology at the University of British Columbia in Vancouver, BC, Canada. Her co-authors include Elizabeth B. Kujawinski, Department of Marine Chemistry and Geochemistry; Sarah B. Das, Department of Geology and Geophysics; Crystaline F. Breier, Department of Marine Chemistry and Geochemistry; Paul Henderson, Department of Marine Chemistry and Geochemistry; and Matthew A. Charette, Department of Marine Chemistry and Geochemistry, all of WHOI.

This research was supported by the WHOI Clark Arctic Research Initiative, the National Science Foundation, the WHOI Ocean and Climate Change Institute, and an AGU Horton Hydrology Grant.


The Woods Hole Oceanographic Institution is a private, non-profit organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the oceans and their interaction with the Earth as a whole, and to communicate a basic understanding of the oceans’ role in the changing global environment. For more information, please visit the WHOI website.

Wildwind 2016 660x82Barz Optics - San Juan Worlds Best EyewearNaiad/Oracle Supplier

Related Articles

Frigid flying – Coast Guard aircrews take on New England Winter
Freezing rain? Teeth-chattering temperatures? Limited visibility? Coast Guard aircrews are still ready to fly. Freezing rain? Teeth-chattering temperatures? Limited visibility? Coast Guard aircrews are still ready to fly. At Air Station Cape Cod, aviation maintenance and electronic technicians work around the clock to ensure the MH-60 Jayhawk helicopters are prepared and ready to launch. There is one thing the maintenance crews and pilots cannot control: winter weather.
Posted on 9 Feb
When whales meet sails
CAMPER helmsman Roberto ‘Chuny’ Bermudez found himself nearly face to face with whale in middle of North Atlantic Ocean. Currently the database for marine mammal strikes is very sparse. We are requesting sailors and boaters help to submit information on current and past incidents, however long ago that may be. By giving a location, date, identification if possible, and any other relevant information you can help scientists better understand where marine mammals are at risk for strikes
Posted on 8 Jan
Vendée Globe – Uncertainty about weather condition in North Atlantic
Alex Thomson and Armel le Cléac'h are probably looking closely at the wind models for the North Atlantic. Alex Thomson and Armel le Cléac'h are probably looking closely at the wind models for the North Atlantic. It does not seem to be easy.
Posted on 4 Jan
10,000 metric tons of plastic enter Great Lakes every year
A new study inventories and tracks high concentrations of plastic in Great Lakes could help inform cleanup efforts A new study by Rochester Institute of Technology that inventories and tracks high concentrations of plastic in the Great Lakes could help inform cleanup efforts and target pollution prevention.Researchers found that nearly 10,000 metric tons—or 22 million pounds—of plastic debris enter the Great Lakes every year from the United States and Canada.
Posted on 2 Jan
The Deepwater Horizon aftermath
Researchers analyze 125 compounds from oil spilled in Gulf of Mexico to determine their longevity at different levels. Researchers analyze 125 compounds from oil spilled in the Gulf of Mexico to determine their longevity at different contamination levels. The oil discharged into the Gulf of Mexico following the explosion and sinking of the Deepwater Horizon (DWH) rig in 2010 contaminated more than 1,000 square miles of seafloor.
Posted on 1 Jan
What happened to Deepwater Horizon Oil?
What happened to the 160 million gallons of oil that gushed for 87 days into the Gulf of Mexico in 2010? Six years after the Deepwater Horizon oil spill, we are continually asked two questions. What happened to the 160 million gallons of oil that gushed for 87 days into the Gulf of Mexico in 2010? Was discharging 1.67 million gallons of chemicals into the ocean to disperse the oil a good or bad idea?
Posted on 24 Dec 2016
Vendée Globe – Light winds for Banque Populaire and Hugo Boss
The first one to get out of it will have a nice north-westerly flow on the edge of the high pressure system. Banque Populaire and Hugo Boss are sailing in a complex weather system in a light wind zone. The first one to get out of it will have a nice north-westerly flow on the edge of the high pressure system.
Posted on 15 Dec 2016
Great Barrier Reef managers and industry prepare for summer
Marine park managers, scientists and experts recently met for the annual pre-summer workshop Marine park managers, scientists and experts recently met for the annual pre-summer workshop to assess climate-related risks to the Great Barrier Reef over the coming months. Current predictions by the Bureau of Meteorology and National Oceanic and Atmospheric Administration are for a summer of average sea temperatures across the Great Barrier Reef.
Posted on 7 Dec 2016
Fourth Blog from on board Perie Banou II
Oh no - not the coffee cup Oh no - not the coffee cup - Jon keeps us all entertained as he approaches Reunion Island. The B&G chartplotter tells me since leaving the pleasant mid Western Australian town of Carnarvon (by world standards, an isolated town), that I have sailed some 2559 NM and have 751nm to go to Le Port Reunion Island. French. Reunion is a Suburb (department) of Paris. Population 844,000.
Posted on 23 Nov 2016
Third Blog from onboard Perie Banou II
Wind over the last week has been quiet and mild - Trade Winds from South East and South South East. It is 0830am here. 1030 in Western Australia. Windy. Rather Windy. Wind over the last week has been quiet and mild - Trade Winds from South East and South South East. Barometer 1018 to 1020 whatever they are. Last night I tapped the barometer and it sorta went oops. 1015hPa. Blimey.
Posted on 18 Nov 2016