Icebergs as a source of nutrients

November 20, 2019

Sea creatures, whether large or small, need nutrients. The supply mechanism delivering these nutrients is very different in different parts of the ocean, there are nutrient-rich coastal areas, but also very nutrient-poor regions in the open ocean. In some areas, the lack of iron in seawater limits plankton growth. These include much of the polar oceans. Here, icebergs appear to be an important source of iron input, which could increase due to increased iceberg production as a result of climate change. So far, however, only a limited amount of data has been available to estimate this process. An international team of researchers led by GEOMAR Helmholtz Centre for Ocean Research Kiel has now examined ice samples worldwide for their iron content. The results show that an increase in icebergs, for example due to global warming, does not necessarily lead to an increase in iron input into the oceans. The results of their study were published today in the international journal Nature Communications.

"In cooperation with partners at the IDEAL Centre for Oceanography in Chile, Greenland, Iceland and Spitsbergen, we have collected a large collection of ice samples from a large number of large maritime glaciers around the world", explains lead author Dr. Mark Hopwood from GEOMAR. These samples were then analysed for trace substances in clean room laboratories. The sampling itself poses a particular challenge. Not only because the samples come from regions that are difficult to access. "Approaching an iceberg floating in the water with a small boat is not safe and requires a lot of experience", says Mark Hopwood. "While we were collecting samples in the coastal waters around Spitsbergen, we saw a relatively small iceberg suddenly break into two halves and turn around in the water. If this happens to a large iceberg that is being sampled from a boat, it can be very dangerous", continues Dr. Hopwood.

The analyses initially showed, to a certain extent surprisingly, in most samples no major differences in the composition of the ice from different locations, i.e. the iron content in ice from Greenland is not significantly different from that in Patagonia. However, the ice of a single iceberg can be very different. The pure ice contains very little iron, but ice that is heavily loaded with sediment, much more than one would find in a river, for example. These differences in iron concentration are enormous and can be in the order of a million fold. About 4% of the ice samples collected contained more than 90% of the total iron.

What does this mean for biology? "Well, the general hypothesis was that increasing the number of icebergs swimming in the sea would increase the fertilising effect. But our work shows that things are a little more complicated, because most ice has no strong fertilizing effect, the 4% of the ice with most of the iron will probably have a much stronger fertilizing effect than the rest of the 'clean' ice", Mark Hopwood sums up. So the origin and dynamics of the "dirty" ice play a really important role in how much the ice in a region, or from a glacier, can (or cannot) change primary production in the ocean.

"Unfortunately, many questions remain unanswered. For example, where this sediment rich ice comes from, how it varies globally and in what spatial and temporal dimensions it releases iron through melting processes in the ocean", Hopwood concludes.
-end-


Helmholtz Centre for Ocean Research Kiel (GEOMAR)

Related Climate Change Articles from Brightsurf:

Are climate scientists being too cautious when linking extreme weather to climate change?
Climate science has focused on avoiding false alarms when linking extreme events to climate change.

Mysterious climate change
New research findings underline the crucial role that sea ice throughout the Southern Ocean played for atmospheric CO2 in times of rapid climate change in the past.

Mapping the path of climate change
Predicting a major transition, such as climate change, is extremely difficult, but the probabilistic framework developed by the authors is the first step in identifying the path between a shift in two environmental states.

Small change for climate change: Time to increase research funding to save the world
A new study shows that there is a huge disproportion in the level of funding for social science research into the greatest challenge in combating global warming -- how to get individuals and societies to overcome ingrained human habits to make the changes necessary to mitigate climate change.

Sub-national 'climate clubs' could offer key to combating climate change
'Climate clubs' offering membership for sub-national states, in addition to just countries, could speed up progress towards a globally harmonized climate change policy, which in turn offers a way to achieve stronger climate policies in all countries.

Review of Chinese atmospheric science research over the past 70 years: Climate and climate change
Over the past 70 years since the foundation of the People's Republic of China, Chinese scientists have made great contributions to various fields in the research of atmospheric sciences, which attracted worldwide attention.

A CERN for climate change
In a Perspective article appearing in this week's Proceedings of the National Academy of Sciences, Tim Palmer (Oxford University), and Bjorn Stevens (Max Planck Society), critically reflect on the present state of Earth system modelling.

Fairy-wrens change breeding habits to cope with climate change
Warmer temperatures linked to climate change are having a big impact on the breeding habits of one of Australia's most recognisable bird species, according to researchers at The Australian National University (ANU).

Believing in climate change doesn't mean you are preparing for climate change, study finds
Notre Dame researchers found that although coastal homeowners may perceive a worsening of climate change-related hazards, these attitudes are largely unrelated to a homeowner's expectations of actual home damage.

Older forests resist change -- climate change, that is
Older forests in eastern North America are less vulnerable to climate change than younger forests, particularly for carbon storage, timber production, and biodiversity, new research finds.

Read More: Climate Change News and Climate Change Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.