Do you know if that includes *freshwater* ice?
There's a comprehensive and quite readable discussion of every aspect of Arctic freshwater in Chapter 7 of the assessment. By freshwater, oceanographers don't mean drinking water fresh, merely how not-as-saline as 34.8 psu seawater. So 34.7 psu is already freshened by how much water would have to evaporate to bring it up to 34.8 psu. The surface freshwater anomaly extends down a few tens of meters at most (first image).
First year ice is still quite salty -- not single ice crystals per se which are standard ice Ih with no inclusions -- but from extruded salt in brine channels that's still around. Thus the Russian 'Barneo' expedition this year had to melt snow to get their drinking water. By some accounts, a 2:3 mix of salt:fresh is utilizable by humans.
Below, some scattered snippets from Chapter 7. The attached figures are better viewed in the original.
Snow, Water, Ice and Permafrost in the Arctic (SWIPA) 2017
Arctic Monitoring and Assessment Program (AMAP), Oslo, 2017 [cutoff date mid-2016]
http://www.amap.no/documents/download/2987The Arctic water cycle is expected to continue to intensify during this century. Mean precipitation and daily precipitation extremes will increase over mid- and high latitudes, with implications for the management of water resources, flow of freshwater into the Arctic Ocean, changes in sea ice temperature, and amplification of regional warming (through reduced surface reflectivity caused by a shift from snow to more rain in the warmer seasons).
The areal reduction of old sea ice has consequences for mean sea-ice thickness, thickness distribution, and surface roughness of Arctic sea ice (Hansen et al., 2014; Renner et al., 2014; Landy et al., 2015). Reduced ice thickness is related to changes in the forcings, whereas changes in thickness distribution are directly related to the properties of the different ice classes present.
Younger sea ice has on average higher salinity than older ice, and this has various consequences, for example how much freshwater is transported with drifting ice and on habitat conditions for organisms living within the ice.
A shift from perennial sea ice to predominantly seasonal ice types will cause changes in the physical properties of the ice cover. These changes are mainly associated with the volume of brine trapped within the ice. In contrast to first-year ice, multi- year ice has undergone a summer melt season and in the process lost most of the brine trapped within.
The brine volume, which can be calculated as a function of salinity and temperature, determines the porosity of the ice, which controls many important properties of sea ice, such as its strength, thermal and dielectric properties, mass (chemical and gas) transport, and the development of melt ponds and surface albedo.
Salt and heat fluxes are affected by the increased presence of first-year sea ice. First-year ice growth rates are higher than for older ice types, which means more salt is released during autumn and winter ice growth. In summer, the higher melt rates for first- year ice increases freshwater input to the surface ocean, thereby increasing buoyancy flux and stratification. Gas exchange rates through sea ice are also changing: more saline ice means more active exchange processes because gas permeability is higher in more porous sea ice.
In contrast to the southern hemisphere, the configuration of continents in the northern hemisphere is such that they effectively capture moisture from the atmospheric storm tracks of the Westerlies and redirect in north-flowing drainage basins disproportionate quantities of freshwater into the Mediterranean configuration of the Arctic Ocean (Figure 7.1).
Hence, while the Arctic Ocean represents only 1% (in terms of volume) and 3% (in terms of surface area) of the global ocean, it collects over 11% of the global river discharge (Dai and Trenberth, 2002; Carmack et al. 2016). e Trade Winds also transport moisture from the Atlantic Ocean across the Isthmus of Panama to freshen the Pacific Ocean, and some of this freshened water eventually flows into the Arctic Ocean through Bering Strait. e resulting salt stratification or halocline (i.e. a freshened upper ocean and salinity increasing with depth) is the dominant characteristic of high-latitude seas in general and the Arctic Ocean in particular .
The freshwater budget of the Arctic Ocean is governed by the system’s key functions and processes: 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;
The Arctic Ocean freshwater budget was recently updated by Haine et al. (2015) (Table 7.1). The distribution of freshwater within the Arctic Ocean is heterogeneous and controlled by circulation and water mass structure. The Arctic Ocean is made integral to the global ocean by the northern hemisphere thermohaline circulation which drives Pacific Water through Bering Strait into Canada Basin, and counter-flowing Atlantic Water through Fram Strait and across the Barents Sea into Nansen Basin.
Following Bluhm et al. (2015), it is useful to recognize four vertically-stacked circulation layers (Figure 7.5): (1) the wind- driven surface layer circulation that is characterized by the cyclonic Trans-Polar Dri from Siberia to Fram Strait and the anticyclonic Beaufort Gyre in southern Canada Basin; (2) the underlying circulation of waters that comprise the halocline complex, composed largely of Pacific Water and Atlantic Water that are modified during their passage over the Bering/ Chukchi and Barents/Siberian shelves, respectively; (3) the topographically-trapped Arctic Circumpolar Boundary Current that carries Atlantic Water cyclonically around the boundaries of the entire suite of basins; and (4) the very slow exchange of Arctic Ocean Deep Waters.
Within the basin domain two water mass assemblies are observed, the difference between them being the absence or presence of Pacific Water sandwiched between Arctic Surface Waters above and the Atlantic Water complex below; the boundary between these domains forms the Atlantic/Pacific halocline front.
But the distribution of freshwater within the Arctic Ocean is not uniform, and salinities range from about 35 where Atlantic Water enters the basin to near zero adjacent to river mouths and along the coast (Carmack et al., 2016). is huge range in salinity, the main parameter that determines density stratification in high-latitude oceans, affects almost every aspect of circulation and mixing within the Arctic Ocean.
Relative to a reference salinity of 34.8, about 101,000 km3 of freshwater are stored in the Arctic Ocean (this is an estimate of the 2000–2010 annual average volume by Haine et al., 2015; Table 7.1). The largest freshwater reservoir exists in the Amerasian Basin, specifically in the Beaufort Gyre where about 23,500 km3 freshwater are stored and the accumulated freshwater anomaly diluting the upper ocean above the 34.8 isohaline surface is about 20 m thick. In the Eurasian Basin, typical liquid freshwater thicknesses are 5–10 m.
Freshwater in the solid phase as sea ice is another important reservoir in the Arctic. About 14,300 km3 of freshwater are stored in sea ice (2000–2010 average from Haine et al., 2015). e largest sea ice volumes are north of the Canadian Arctic Archipelago and Greenland and across the pole, where the ice is still relatively thick (Kwok et al., 2009).
The seasonal freeze-thaw cycle acts to exchange freshwater between the liquid and solid phases. Its amplitude is about 13,400 km3 (averaged over the decade of the 2000s; Haine et al., 2015), close to the annual average freshwater volume stored in sea ice. Sea-ice formation in winter occurs throughout the Arctic Ocean but the prevailing currents tend to export ice frozen over the Eurasian shelves toward the central Arctic and the Trans-Polar Drift (Figure 7.5).
Under current climate conditions only about 35% of the sea ice present at the end of winter, when the ice volume peaks survives the summer to become multiyear ice. Of the remaining 65%, most melts within the Arctic although some is exported south.
Kwok and Rothrock (2009) reported submarine and satellite data that show the average end-of-melt season ice thickness was 3.02 m in 1958–1976 but just 1.43 m in 2003–2007. Because both ice extent and ice thickness are declining, sea-ice volume is also declining.
Currently, the Arctic Ocean is freshening (Haine et al., 2015), warming (Polyakov et al., 2012), losing sea ice (Stroeve et al., 2012), and its ice cover is changing properties and moving faster (Kwok et al., 2013).