Adaptation Actions for a Changing Arctic: Perspectives from the Barents Area

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Chapter 4 · Physical and socio-economic environment

Surface water from the NorthAtlantic entering the Nordic Seas is presently equilibrated with respect to atmospheric CO 2 and carries a small or zero capacity for further uptake (Olsen et al., 2006). A timeline of carbon chemistry from Ocean Weather Station Mike (66°N 2°E) reveals an annual change in pH of -0.001 pH-units per year in surface water between 2001 and 2005 (Skjelvan et al., 2008). In this respect, it is important to remember that the pH scale is logarithmic. The surface waters of the Arctic Ocean, with low temperature and high natural concentrations of inorganic carbon are expected to become under-saturated with respect to aragonite (a common form of calcium carbonate) within a few decades (Steinacher et al., 2009). In fact,Arctic surface waters are already under-saturated in some areas for parts of the year, especially over the continental shelves (Chierici and Franson, 2009; Steinacher et al., 2009).Models have become an important tool for investigating the effect of further increase in atmospheric CO 2 in a future climate.Using downscaled physics from a GCM to force an ecosystem model, Skogen et al. (2014) compared the simulated carbonate system in 2000 and 2065 under the A1B scenario in the Nordic and Barents seas. They found the aragonite saturation state of seawater would evolve,with under- saturated bottomwaters shoaling by about 1200m in the Nordic Seas (from 3000 m to 1800 m) and a large increase in the areal extent of under-saturated surface waters. Surface water pH fell by 0.19 pH-units between 2000 and 2065, while the model showed the annual CO 2 air–sea flux in the Barents Sea almost doubled over this period, from 23 to 37 gC/m 2 . 4.3.6 Icebergs Sea ice and icebergs are two distinctive ice forms at high latitudes. While sea ice forms under cold conditions when the upper layer freezes, icebergs are generated when glaciers calve and disintegrate, often associated with warming episodes, and may represent a hazard to shipping and offshore activities (Sharp et al., 2011). See Section 4.4.3 and CliC/AMAP/IASC (2016) for more information concerning glaciers. The main sources of Barents Sea icebergs are glaciers on Svalbard, Franz Josef Land, and Novaya Zemlya and some other Arctic islands (Ushakov and Victoria) (Walsh et al., 2005; Kubyshkin et al., 2006). Iceberg calving accounts for 30% of glacier reduction on Franz Josef Land (Koryakin,1988).There is limited information on icebergs, because there is no universal model for predicting their presence, and climate change projections do not include icebergs calved from glaciers. The number of icebergs varies from year to year, and Abramov (1992) found a correlation between the southern limit of the sea ice and the southward extension of the icebergs in the Barents Sea, based on navigation and aircraft monitoring of icebergs between 1933 and 1990.The southwardmovement in both ice formsmay be explained by a predominance of northerly and northeasterly winds.Abramov also found an increase in the number of iceberg reaching further south over the 57-year study period. Kubyshkin et al. (2006) attributed a big tabular iceberg detected in the ShtokmanGas Condensed Field in 2003 to outlet glaciers on Franz‑Josef Land. The number of icebergs observed in the Barents Sea between 1928 and 2007 showed pronounced year-to-year variability (Zubakin et al., 2007),with fewer icebergs observed before 1950

also a major factor in the Baltic Sea region. Simpson et al. (2015) observed that relative sea level projections can differ by as much as 0.50 m from place to place depending on vertical uplift rates. Analysis of changes in local sea level must take into account the glacial isostatic effect.The adjustment-corrected rate from Arctic tide gauges for the period 1993–2014 varies along the Norwegian mainland: Vardø (2.7±1.6 mm/y), Honningsvåg (2.9±1.6 mm/y), Hammerfest (3.8±1.7 mm/y), Tromsø (3.7±1.8 mm/y), Andenes (3.7±1.7 mm/y), Harstad (3.4±1.7 mm/y), Kabelvåg (4.0±1.8 mm/y), and Bodø (3.3±2.0 mm/y). Future wave conditions in the Barents Sea will depend on surface wind and ice conditions, and the open sea is subject to strong wind fetch (Lynch et al., 2008). Based on model simulations for the 21st century, Khon et al. (2014) reported a significant increase in wave height across the Arctic due to reduced sea-ice cover and stronger regional winds.An opposite tendency, a slight reduction in wave height, may appear over the Atlantic sector and Barents Sea. Rutgersson et al. (2015) found no trend in wind statistics, but pronounced decadal variations. An important implication of stronger wave-induced vertical mixing under ice-free conditions is a deepening of the upper mixed layer and a rise in salinity due to the influx of deeper more-saline water (Kraus and Turner, 1967). This additional salt flux from below may partly compensate for the additional freshwater input through increased precipitation. This could result in a spatially intermittent weakening of vertical density stratification accompanied by localized winter convection rather than massive overturning events. 4.3.5 Ocean acidification Many marine species incorporate calcium carbonates into their body armor (shells, exoskeletons, claws). Ocean acidification leads to less favorable conditions for the formation of these mineral-based features. Currently, surface waters are generally supersaturated with respect to calcium carbonates, but saturation state decreases when more CO 2 is dissolved in the water. Understanding how saturation state could change with respect to these minerals is therefore important for understanding how ocean acidification might impact future ecosystems. The average pH of surface waters in the global oceans has decreased from about 8.2 before the onset of the industrial revolution to a present-day average of about 8.1 (Caldeira and Wickett, 2003; Orr et al., 2005). This ocean acidification (i.e. fall in pH) is due to the dissolution of CO 2 , and corresponds to about one third of the CO 2 released to the atmosphere from fossil fuel combustion, cement production, and changes in land use (Canadell et al., 2007).Oceanic uptake of atmospheric CO 2 is influenced by ice cover, biological productivity, surface water temperature and ocean circulation.A longer ice-free period and a decrease in ice extent will increase the air-sea carbon flux, especially through increased biological productivity (Sakshaug, 2004; Wassmann et al., 2006). However, warming of surface waters also decreases CO 2 solubility (e.g. Kaltin et al., 2002) and reduced deep water formation will slow the transport of CO 2 into the deeper ocean.