Respiratory disorder in the ocean: Team demonstrates the influence of eddies on the oxygen sustenance

Nov 18, 2013
Eddy distribution from satellite data of the sea surface height anomaly at mid-November 2012 (top) and oxygen distribution across the anticyclonic eddy (bottom). Source: GEOMAR

For more than four months, from Nov. 2012 to March 2013, Kiel ocean scientists investigated on the German research vessel METEOR the oxygen-poor upwelling regions in the tropical Pacific off Peru. First results of the project carried out in the context of the Collaborative Research Centre (SFB) 754 "Climate-biogeochemistry interactions in the tropical ocean" show how eddies in the ocean influence the oxygen and nutrient distribution in the oxygen-poor regions.

Observations show that in large regions of the tropical oceans, the so-called minimum zones (OMZ), the declined during the last decades. In addition the ocean emitted increasingly climate relevant trace gases to the atmosphere. Based on numerical models it was speculated, that small-scale circulation pattern - so-called - influence sustainably the distribution of oxygen and nutrients in the OMZ's. It is known that in the ocean, eddies with different rotation direction exist similar to high and low pressure cells in the atmosphere which can be observed as sea surface elevation anomalies from satellite data. In contrast to the atmosphere ocean eddies only have a horizontal diameter of 80 to 200 km and the rotation speed is distinctly lower with less than 30 cm/s. Due to the high heat capacity and density of seawater heat and property transport in eddies are considerably important for the nutrient distribution and hence the basis of life in the .

Guided by real-time satellite data of sea surface height anomalies three eddies could be identified in the region off Peru and intensely sampled during METEOR expedition M90 in November 2012. "Our observations show that eddies transport water with strong differences compared to the surrounding waters in temperature, salinity, oxygen and nutrients while moving westwards with a few centimetres per second", explains the lead author of this study Dr. Lothar Stramma from GEOMAR. "As the eddies dissipate after some weeks to months anomalies of these properties are introduced as disturbances into the open ocean and hence are responsible for surprisingly high productivity in the normally nutrient-poor open ocean", Stramma states. "Near the Peruvian shelf we observed in eddies enhanced chlorophyll concentrations as well as strong nutrient loss, e.g. of nitrate", co-author Prof. Hermann Bange explains. During the cruise co-author Alberto Lorenzo from the Peruvian partner institute IMARPE measured pH-values of the water and hence the acidity of the ocean. He could show that the acidity of sea water, which has a large influence on biological processes, changes in eddies. In anticyclonic eddies (turning counterclockwise in the southern hemisphere) the vertical extend of water with low pH, hence higher acidity increased.

From earlier investigations of the SFB-754 it is known, that in the equatorial southeast Pacific the 'breath of the ocean' (the supply and loss of oxygen in the oxygen-poor regions) is carried out mainly by zonal ocean currents while the results of this study show that on the poleward side of the oxygen minimum zone of the southeast Pacific eddies are responsible for a considerably contribution for changes in oxygen and nutrient distribution. "Thus, the results are of particular importance as they help to improve model computations to better predict future expansions of low oxygen areas in the " Dr. Stramma sums up.

Explore further: Scientists warn of hot, sour, breathless oceans

More information: Stramma, L., Bange, H.W., Czeschel, R., Lorenzo, A., Frank, M.: On the role of mesoscale eddies for the biological productivity and biogeochemistry in the eastern tropical Pacific Ocean off Peru, Biogeosciences, 10, 7293-7306, DOI: 10.5194/bg-10-7293-2013

add to favorites email to friend print save as pdf

Related Stories

Decoding material fluxes in the tropical ocean

Aug 02, 2013

How is vital oxygen supplied to the tropical ocean? For the first time, oceanographers at GEOMAR Helmholtz Centre for Ocean Research Kiel were able to make quantitative statements regarding this question. ...

Mesoscale ocean eddies impact weather, study shows

Jul 07, 2013

Not only large-scale ocean currents impact weather but also relatively small eddies, as a new study by scientists at ETH Zurich reveals. The researchers therefore recommend to account for these eddies in ...

Scientists warn of hot, sour, breathless oceans

Nov 14, 2013

Greenhouse gases are making the world's oceans hot, sour and breathless, and the way those changes work together is creating a grimmer outlook for global waters, according to a new report Wednesday from 540 ...

A swirling oasis of life

Feb 14, 2012

A serpentine eddy swirls in the southern Indian Ocean several hundred kilometers off the coast of South Africa in this natural-color image, acquired by NASA’s Terra satellite on December 26, 2011.

Recommended for you

Sculpting tropical peaks

17 hours ago

Tropical mountain ranges erode quickly, as heavy year-round rains feed raging rivers and trigger huge, fast-moving landslides. Rapid erosion produces rugged terrain, with steep rivers running through deep ...

Volcano expert comments on Japan eruption

18 hours ago

Loÿc Vanderkluysen, PhD, who recently joined Drexel as an assistant professor in Department of Biodiversity, Earth and Environmental Science in the College of Arts and Sciences, returned Friday from fieldwork ...

User comments : 0