Discharge of Total Nitrogen and Phosphates
One of the objectives for the River Challenge of the Sea Basin Checkpoint Arctic project is to provide time series of the annual input of Total Nitrogen and Phosphates into the Arctic Ocean.
Water quality measurements like Phosphorus and Nitrogen data are rather scarce for Arctic Rivers. A variety of Assessment Reports, most commonly primary literature, are publicly available for both Nitrogen and Phosphorus. Most identified Assessment Reports are primarily literature articles which contained very specific data, of low spatial extend for a limited duration. It is not, or at least not easily feasible to combine these data into a coherent and consistent data set for the panarctic watershed. One data set is an exception to this and provides a consistent set of data for the largest rivers in the Arctic is the Arctic Great Rivers Observatory (Arctic-GRO) data set. This data set contains measurements of different forms of Phosphorus and Nitrogen as well as a variety of chemical constituents. This database focusses on the six largest rivers, this source and other sources however did not focus significantly on the smaller rivers. The data found at the Arctic-GRO focuses primarily on the past few years and seems to be increasing over time. This data has also already been post processed and the laboratory techniques are described in detail. The main problem with this Arctic Great Rivers Observatory site is that although a variety of chemical constituents are measured over time, it is difficult to calculate the Total Nitrogen and Total Phosphorus from the measurements noted. Total Nitrogen is the sum of the total dissolved nitrogen (TDN) and particulate organic nitrogen (PON). Total dissolved nitrogen is the sum of nitrate-N, nitrite-N and ammonia-N. Total Phosphorous is the sum of the total dissolved phosphorus and particulate phosphorus. The particulate phosphorus is not in the dataset, therefore the total dissolved phosphorus is best representation of the total phosphorus in this dataset.
The “Big 6” (the Ob’, Yenisey, Lena, Mackenzie, Yukon and Kolyma) cover 67% of the pan-Arctic watershed into the Arctic ocean. The next eight largest rivers and their watersheds together only cover an additional 11% of this area and 16% of the discharge, with 22% of the area and 21% of the discharge left for the remaining ‘smaller rivers’ of the Arctic (R.M. Holmes et al., 2013).
Although in terms of water discharge one could say that the largest rivers provide enough information to achieve pan-Arctic synthesis the same cannot be said with regards to water chemistry and the fluxes of nutrients into the Arctic ocean from Arctic rivers. This is because the biggest 14 Arctic river watersheds cover vastly lower area percentages of tundra and (continuous) permafrost compared to the remaining watersheds, with the latter showing disproportionate higher percentages of such tundra and permafrost relative to its watershed area size (R.M. Holmes et al., 2013). These remaining watershed areas are mostly significant high-latitude watershed areas which are located closer to Arctic coastline where the land-to-sea solute fluxes and run-off regimes act significantly different on the Arctic ocean system and yield relatively larger nutrient mass loadings to the Arctic ocean (Destouni, Hannerz, Prieto, Jarsjö, & Shibuo, 2008; R.M. Holmes et al., 2013). These differences between larger watersheds and the remaining watersheds mean that accurate extrapolation from the first to the latter to achieve synthesis and understanding of the biogeochemical fluxes between the pan-Arctic watershed and the Arctic ocean is impossible.
Although the monitoring of land-to-sea fluxes has recently improved due to the data from the Arctic-GRO project, relatively large and potentially significant high-latitude coastal areas remain unmonitored. Systematic near-coastal gaps in watershed areas in the monitoring of freshwater discharges to the sea introduce significant bias in the quantification of coastal land-to-sea nutrient mass loading (Bring & Destouni, 2009; R.M. Holmes et al., 2013). The gaps in the monitoring of near-coastal areas are increasingly becoming important as they are likely to involve the most degree of changes in land-to-sea nutrient fluxes due to climate change. Climate change will disproportionately affect the permafrost and subsequently the land-to-sea nutrient fluxes from these permafrost areas. Next, climate change will increase the total discharge (Peterson et al., 2002) and accessibility to natural resources and the Northern sea routes and thus will increase economic activity and anthropogenic pressure along the Arctic coastline due to establishment of human populations (Bring & Destouni, 2009). Furthermore, the significant dissimilarity between characteristic properties of monitored and unmonitored areas limit the possibility to generalize hydrological and hydrochemical impact assessments based on monitoring data. These dissimilarities in hydrological and hydrochemical properties between areas with regards to permafrost extent, vegetation type and climatic condition can become much larger with the upcoming climate change. Other factors make it difficult at present to achieve synthesis with regards to Arctic water-chemistry nutrient land-to-sea fluxes, including shorter time series, unharmonized data, inter- and even intra-continent discrepancies in measurement methods and restricted accessibility due to lack of cooperation between pan-Arctic nations (McClelland, Tank, Spencer, & Shiklomanov, 2015).
A literature analysis shows several recommendations with regard to achieving coordinated and sustainable water-chemistry monitoring of the pan-Arctic watershed area:
- Establishment of an agreement between monitoring agencies of the United States of America, Canada and Russian Federation to set-up and maintain long-term coupled river discharge monitoring with water quality monitoring efforts from existing water discharge gauge locations in the six large Arctic rivers (McClelland et al., 2015). This increases knowledge on past trends and contemporary fluxes to set a baseline to identify changes in long-term developments in increasing river discharge and land-to-sea nutrient fluxes due to climate change in the Arctic drainage area.
- Establishment of an international river observing coordination board with partners from all Arctic countries from governmental agencies, scientific community and other stakeholders within the pan-Arctic drainage area. This coordination board should establish and dictate rules for an international repository for water chemistry monitoring data, thereby providing harmonized, up-to-date and good-quality data to environmental modelers and policy makers (Bring & Destouni, 2009; McClelland et al., 2015). – The pan-Arctic overarching Arctic-HYCOS project currently focusses on water discharge, temperature and sediment transport, leaving water quality for a later stage. Data exchange standards between nations are also implemented in a later stage. (WHYCOS, 2017).
- Enable an internationally accepted system for Arctic measurement and analysis methods and enable inter-laboratory collaboration and comparisons of water quality analyses to ensure reliable and comparable results among regions and continents and achieve greater understanding of previously collected data (McClelland et al., 2015). This helps in providing a baseline for improving and calibration of international Arctic biogeochemical models.
- Through an efficient investigative methodology extending monitoring efforts in high-altitude areas and near-ocean areas in both medium sized and small sized river systems to fully understand Arctic riverine biogeochemistry at different scales and systems. This knowledge can then be used to extrapolate on the remaining unmonitored areas in the pan-Arctic watershed (Bring & Destouni, 2009).
- Increased attention of the scientific community on estuarine, coastal and estuarine processes that affect the impact of fluvial inputs on the biogeochemistry of the Arctic ocean, as well as on the coastal zone of the Arctic. This is to establish a greater understanding of the extensive processing of fluvial nutrients fluxes in the coastal zone before they reach the open ocean (R M Holmes et al., 2000; Robert Max Holmes et al., 2012; McClelland et al., 2015).
- Improving the mechanistic understanding of tightly coupled atmospheric, terrestrial and aquatic components of the Arctic watershed area to establish a strong modelling basis for understanding of the current rates of changes and projections of future changes due to climate change and its impact on the Arctic ocean (R.M. Holmes et al., 2013).
- Bring, A. and Destouni, G. (2009) ‘Hydrological and hydrochemical observation status in the pan-Arctic drainage basin’, Polar Research. Blackwell Publishing Ltd, 28(3), pp. 327–338. doi: 10.1111/j.1751-8369.2009.00126.x.
- Destouni, G. et al. (2008) ‘Small unmonitored near-coastal catchment areas yielding large mass loading to the sea’, Global Biogeochemical Cycles, 22(4). doi: 10.1029/2008GB003287.
- Holmes, R. M. et al. (2000) ‘Flux of nutrients from Russian rivers to the Arctic Ocean: Can we establish a baseline against which to judge future changes?’, Water Resources Research, 36(8), pp. 2309–2320. doi: 10.1029/2000WR900099.
- Holmes, R. M. et al. (2012) ‘Seasonal and Annual Fluxes of Nutrients and Organic Matter from Large Rivers to the Arctic Ocean and Surrounding Seas’, Estuaries and Coasts, 35(2), pp. 369–382. doi: 10.1007/s12237-011-9386-6.
- Holmes, R. M. et al. (2013) ‘Climate change impacts on the hydrology and biogeochemistry of Arctic Rivers’, in C. R. Goldman, M. Kumagai, and R. D. R. (ed.) Global Impacts of Climate Change on Inland Waters. Wiley.
- McClelland, J. W. et al. (2015) ‘Coordination and Sustainability of River Observing Activities in the Arctic’, Arctic. Arctic Institute of North America, pp. 59–68. doi: 10.2307/43871387
- McClelland, J. W., et al. (2016), Particulate organic carbon and nitrogen export from major Arctic rivers, Global Biogeochem. Cycles, 30, 629–643, doi:10.1002/2015GB005351.
- Peterson, B. J. et al. (2002) ‘Increasing river discharge to the Arctic Ocean.’, Science (New York, N.Y.). American Association for the Advancement of Science, 298(5601), pp. 2171–3. doi: 10.1126/science.1077445.
- WHYCOS (2017) Under Implementation: Arctic-HYCOS. Available at: http://www.whycos.org/whycos/projects/under-implementation/arctic-hycos (Accessed: 10 November 2017).