Freshwater and its role in the Arctic Marine System: Sources, disposition, storage, export, and physical and biogeochemical consequences in the Arctic and global oceans

Abstract

The Arctic Ocean is a fundamental node in the global hydrological cycle and the ocean's thermohaline circulation. We here assess the system's key functions and processes: (1) the delivery of fresh and low-salinity waters to the Arctic Ocean by river inflow, net precipitation, distillation during the freeze/thaw cycle, and Pacific Ocean inflows; (2) the disposition (e.g., sources, pathways, and storage) of freshwater components within the Arctic Ocean; and (3) the release and export of freshwater components into the bordering convective domains of the North Atlantic. We then examine physical, chemical, or biological processes which are influenced or constrained by the local quantities and geochemical qualities of freshwater; these include stratification and vertical mixing, ocean heat flux, nutrient supply, primary production, ocean acidification, and biogeochemical cycling. Internal to the Arctic the joint effects of sea ice decline and hydrological cycle intensification have strengthened coupling between the ocean and the atmosphere (e.g., wind and ice drift stresses, solar radiation, and heat and moisture exchange), the bordering drainage basins (e.g., river discharge, sediment transport, and erosion), and terrestrial ecosystems (e.g., Arctic greening, dissolved and particulate carbon loading, and altered phenology of biotic components). External to the Arctic freshwater export acts as both a constraint to and a necessary ingredient for deep convection in the bordering subarctic gyres and thus affects the global thermohaline circulation. Geochemical fingerprints attained within the Arctic Ocean are likewise exported into the neighboring subarctic systems and beyond. Finally, we discuss observed and modeled functions and changes in this system on seasonal, annual, and decadal time scales and discuss mechanisms that link the marine system to atmospheric, terrestrial, and cryospheric systems.

Volume and temperature transports through the main Arctic Gateways: A comparative study between an ocean reanalysis and mooring-derived data

“…We would like to point out that the observation-based volume transport estimate of -0.15 ± 0.06 Sv together with the volume transport by sea 15 ice (-0.07 Sv, derived from -2080 km³/yr (Haine et al, 2015) using 1Sv = 31,536 km³/yr) nicely balances the 0.20 ± 0.08 Sv surface freshwater flux obtained from the inverse-model calculations, as discussed by Tsubouchi et al (2017b). This is also in excellent agreement with the updated surface freshwater flux estimate (0.203 ± 0.016 Sv or 6400 km³/yr, Carmack et al, 2016).…”

Global change in streamflow extremes under climate change over the 21st century

“…This indicates a future increase in the flow volume of the Arctic rivers and increased freshwater inflow into the Arctic Ocean, continuing the trend observed over the last decades (Peterson et al, 2002;Rawlins et al, 2010), which can be attributed to the thaw of permafrost and increased precipitation in a warmer climate. Rivers play a critical role in the Arctic freshwater system (Carmack et al, 2016;Lique et al, 2016), as river runoff is the major component of freshwater flux into the Arctic Ocean (Carmack et al, 2016). Arctic rivers' inflow to the Arctic Ocean accounts for around 10 % of global annual water flux into the oceans (Haine et al, 2015;Lique et al, 2016).…”

“…Climate change is projected to decrease mean runoff in land areas around the Mediterranean and some parts of Europe, southern Africa, and Central and South America, and consequently increase water stress in those regions (Arnell, 2004). It is also projected to worsen aridity in southern Europe and the Middle East, Australia, southeast Asia, and large parts of the Americas and Africa in the 21st century (Dai, 2011).…”

“…Floods and droughts, the natural disasters with the highest cost in human lives (Dilley et al, 2005;IFRC, 2002), are projected to become more intense under anthropogenic global warming and climate change (Dai, 2011;Field, 2012;Stocker et al, 2013). Observational records as well as global climate model (GCM) simulations both show that the amount of water vapor in the atmosphere increases at a rate of approximately 7 % per K of increase in global mean temperature (Allen and Ingram, 2002;Held and Soden, 2006;Wentz et al, 2007), as expected from the Clausius-Clapeyron equation conditional to stable relative humidity (Held and Soden, 2006;Pall et al, 2006).…”

Inorganic carbon fluxes on the Mackenzie Shelf of the Beaufort Sea

“…Distinguishing the ocean acidification signal in the Arctic is complicated because of the interplay of several changing environmental conditions including warming, sea-ice loss, surface freshening and changes in primary production (Carmack et al, 2016). During sampling, a layer of high pCO 2 , low pH water resided at depth on the shelf (Fig.…”