Physical oceanography during POLARSTERN cruise ANT-XII/4

The report presents the results of the CTD measurements carried out in the Bellingshausen Sea - an area rare of CTD measurements. The main part of the report consists of the brief description of the CTD data acquisition and processing routines, the vertical profiles of temperature, salinity and density, and of the plots of the distribution of these properties along the hydrographic sections. The final part of the report deals with the notably similar structure of the vertical density distribution at different locations if presented as a function of a non dimensional vertical co-ordinate. It is pointed out that such a distribution could be an asymptotic limit of stationary mixing along neutral surfaces

Low dissolved Fe and the absence of diatom blooms in remote Pacific waters of the Southern Ocean

The remote waters of the Pacific region of the Southern Ocean are the furthest away from any upstream and upwind continental Fe sources. This prime area for expecting Fe limitation of the plankton ecosystem was studied (March–April 1995) along a north–south transect at ~89°W. At the end of the austral summer the upper wind-mixed layers were in the order of ~100 m deep, thus mixing the algae down into the dimly lit part of the euphotic zone where photosynthesis is severely restricted. The dissolved Fe was found at low concentrations ranging from 0.05 nM near the surface to 0.5 nM in deeper waters. Along the transect (52°S–69°S), the dissolved iron was enhanced in the Polar Front, as well as near the Antarctic continental margin (0.6–1.0 nM). In between, the southern ACC branch was depleted with iron; here the concentrations in surface waters were quite uniform at about 0.21 nM. This is only somewhat lower than the 0.49 nM (October 1992) and 0.31 nM (November 1992) averages in early spring in the southern ACC part of Atlantic 6°W sections. First, the lower ~0.21 nM in March–April 1995 may partly be due to continuation of the seasonal trend where the phytoplankton growth, albeit modest, was removing Fe from the surface waters. Secondly, the 89°W Pacific stations are further downstream continental or seafloor sources than the Atlantic 6°W section. In the latter case, the ACC water had passed through the Drake Passage and also over the Sandwich Plateau. Indeed for Drake Passage, intermediate Fe concentrations have been reported by others. The generally somewhat lower surface water Fe at the ACC and PF at 89°W is consistent with the distance from sources and the late summer. It also would explain the very low abundance of phytoplankton (Chl a) in the region and the conspicuous absence of plankton blooms. In the subAntarctic waters north of the Polar Front there are no diatoms, let alone diatom blooms, due to low availability of silicate. Thus, it appears the biological productivity is suppressed due to iron deficiency, in combination with the severe seasonal effects of wind mixing on the light climate, as well as regional silicate limitation for diatoms.

Data_Sheet_1_Using essential biodiversity variables to assess forest ecosystem integrity.PDF

IntroductionAn unprecedented amount of Earth Observations and in-situ data has become available in recent decades, opening up the possibility of developing scalable and practical solutions to assess and monitor ecosystems across the globe. Essential Biodiversity Variables are an example of the integration between Earth Observations and in-situ data for monitoring biodiversity and ecosystem integrity, with applicability to assess and monitor ecosystem structure, function, and composition. However, studies have yet to explore how such metrics can be organized in an effective workflow to create a composite Ecosystem Integrity Index and differentiate between local plots at the global scale.MethodsUsing available Essential Biodiversity Variables, we present and test a framework to assess and monitor forest ecosystem integrity at the global scale. We first defined the theoretical framework used to develop the workflow. We then measured ecosystem integrity across 333 forest plots of 5 km2. We classified the plots across the globe using two main categories of ecosystem integrity (Top and Down) defined using different Essential Biodiversity Variables.Results and discussion:We found that ecosystem integrity was significantly higher in forest plots located in more intact areas than in forest plots with higher disturbance. On average, intact forests had an Ecosystem Integrity Index score of 5.88 (CI: 5.53–6.23), whereas higher disturbance lowered the average to 4.97 (CI: 4.67–5.26). Knowing the state and changes in forest ecosystem integrity may help to deliver funding to priority areas that would benefit from mitigation strategies targeting climate change and biodiversity loss. This study may further provide decision- and policymakers with relevant information about the effectiveness of forest management and policies concerning forests. Our proposed method provides a flexible and scalable solution that facilitates the integration of essential biodiversity variables to monitor forest ecosystems.</p

Physical oceanography on board of POLARSTERN (1983-11-22 to 2016-02-14)

Measuring temperature and salinity profiles in the world's oceans is crucial to understanding ocean dynamics and its influence on the heat budget, the water cycle, the marine environment and on our climate. Since 1983 the German research vessel and icebreaker Polarstern has been the platform of numerous CTD (conductivity, temperature, depth instrument) deployments in the Arctic and the Antarctic. We report on a unique data collection spanning 33 years of polar CTD data. In total 131 data sets (1 data set per cruise leg) containing data from 10 063 CTD casts are now freely available. During this long period five CTD types with different characteristics and accuracies have been used. Therefore the instruments and processing procedures (sensor calibration, data validation, etc.) are described in detail. This compilation is special not only with regard to the quantity but also the quality of the data - the latter indicated for each data set using defined quality codes. The complete data collection includes a number of repeated sections for which the quality code can be used to investigate and evaluate long-term changes. Beginning with 2010, the salinity measurements presented here are of the highest quality possible in this field owing to the introduction of the OPTIMARE Precision Salinometer