Following the analysis of 207 samples of glacial ice, a study that included experts from Chilean institutions was published in the prestigious journal “Nature Communications,” setting a new precedent for understanding the operation of polar marine systems.
Andrea Navarro, IDEAL Center. Iron is an essential micronutrient for all living organisms. In the oceans, this metal is extremely scarce. Iron acts as a natural fertilizer that increases productivity in marine organisms. As microalgae grow, they consume carbon dioxide (CO2), and produce about 50% of the oxygen used on the planet. This production may be limited by the amount of iron in seawater.
Although this metal is very abundant in the earth’s crust, it is comparatively scarce in the oceans. In the Southern Ocean, in particular, the concentration of iron is even lower, since the Antarctic Circumpolar Current and the westerly winds prevent contributions from other land areas, and the Antarctic ice retains it on the continent.
A new study published in the prestigious journal Nature Communications has revealed that iron is not distributed evenly within icebergs, as scientific literature had assumed for decades, though this was due to lack of evidence. After four years of work and the analysis of the 207 points in Arctic, Patagonian, and Antarctic glacial ice, it was shown that more than 90% of this metal was concentrated in about 4% of the samples analyzed.
Scientists from the GEOMAR – Helmholtz Centre for Ocean Research Kiel in Germany and two Chilean institutions participated in this research. These included the Research Center – Dynamics of High Latitude Marine Ecosystems (IDEAL) of the Austral University of Chile (UACh) and the Pontifical Catholic University of Valparaíso (PUCV). The data obtained in this effort made possible the largest worldwide database of iron concentration in icebergs ever created.
“This work shows that the effect of icebergs on productivity in the oceans depends to a large extent on where sediments and iron-rich layers are located, and how their distribution and abundance change according to the variation in ice shelves,” explained the leader of the study, Dr. Mark Hopwood, GEOMAR chemist and researcher for the IDEAL Center.
Until now, the scientific community has used the “mean” to estimate the effect of icebergs on ocean fertilization. However, researchers now believe that this approach is incorrect.
“Our data show that the relationship between iron and ice masses is much more complex than previously believed. Historically, scientists have calculated the ‘average’ concentration of this metal in icebergs to determine its fertilizing effect. However, thanks to the research we conducted, we realized that this was not a valid method, because as glaciers thaw, their properties change. In the future, we need to observe where the sediment in icebergs comes from,” noted Dr. Juan Höfer, oceanographer and PUCV faculty member, and researcher at the IDEAL Center.
The study represents a milestone for future models, especially in a climate change context, where it is predicted that the flow of glacial ice to the oceans will continue to increase over the next several years.
As a result of this, it is thought that the amount of iron fertilization from icebergs – particularly in the Southern Ocean – will also continue to increase. However, it may do so to a lesser extent than previously believed. Due to this study it is now understood that the fertilizing effect and the flow of glacial ice may not be so simply and directly related.
“The great importance of this study is that the relationship between the fertilizing effect of glaciers and the productivity of the surrounding marine systems differs from what we believed. The glaciers store iron, a micronutrient that limits productivity, affecting the composition and extent of primary producers in marine systems,” concluded Dr. Humberto González, oceanographer and director of the IDEAL Center.