27
relation between the ocean and the sea ice, and any change in
sea ice cover may impact the dynamics and thermodynamics
of the ocean. Recent observations suggest that a diminishing
sea ice cover to the northeast of Svalbard is responsible for
reducing the stratification of the ocean and allowing more
upward heat transfer, which preconditions the ice to further
melting (Polyakov et al. 2010, 2017).
A significant increase in liquid freshwater content has
been observed in the upper Arctic Ocean in the past two
decades (Rabe et al. 2011; Giles et al. 2012; Morison et al.
2012; Rabe et al. 2014), while the Arctic sea ice volume has
been shrinking significantly (Lindsay and Schweiger 2015).
Sea ice and liquid fresh water are important factors for the
Arctic Ocean, where they insulate the atmosphere from the
warm Atlantic-derived water at intermediate depths, by limiting the upward heat transport, hence influencing the sea ice
formation and melting as well as the air temperature.
After a freshening of the subpolar North Atlantic and
Nordic Seas from the 1960s to the 1990s, both regions
became again more saline thereafter (Curry and Mauritzen
2005; Boyer et al. 2007; Mauritzen et al. 2012). The Nordic
Seas and the subpolar North Atlantic are the main regions in
the northern hemisphere, where deep water formation takes
place and thereby are key regions for global climate (Rhein
et al. 2011). Freshwater changes could potentially influence
this overturning system and thereby have a profound impact
on our climate (Koenigk et al. 2007; Rennermalm et al.
2007).
Fig. 2 Arctic summer sea ice
decline (Fetterer et al. 2016,
provided by the National
Snow and Ice Data Center
NSIDC, with permission). (a)
Arctic September (minimum)
sea ice extent in 2016 (white
area) compared to the median
ice edge for the period 1981
to 2010 (fuchsia line) and (b)
average monthly September
sea ice extent for the years
1979–2016, blue line: decline
rate of 13.2% per decade
relative to the 1981–2010
average
The Physical System of the Arctic Ocean and Subarctic Seas in a Changing Climate
relation between the ocean and the sea ice, and any change in
sea ice cover may impact the dynamics and thermodynamics
of the ocean. Recent observations suggest that a diminishing
sea ice cover to the northeast of Svalbard is responsible for
reducing the stratification of the ocean and allowing more
upward heat transfer, which preconditions the ice to further
melting (Polyakov et al. 2010, 2017).
A significant increase in liquid freshwater content has
been observed in the upper Arctic Ocean in the past two
decades (Rabe et al. 2011; Giles et al. 2012; Morison et al.
2012; Rabe et al. 2014), while the Arctic sea ice volume has
been shrinking significantly (Lindsay and Schweiger 2015).
Sea ice and liquid fresh water are important factors for the
Arctic Ocean, where they insulate the atmosphere from the
warm Atlantic-derived water at intermediate depths, by limiting the upward heat transport, hence influencing the sea ice
formation and melting as well as the air temperature.
After a freshening of the subpolar North Atlantic and
Nordic Seas from the 1960s to the 1990s, both regions
became again more saline thereafter (Curry and Mauritzen
2005; Boyer et al. 2007; Mauritzen et al. 2012). The Nordic
Seas and the subpolar North Atlantic are the main regions in
the northern hemisphere, where deep water formation takes
place and thereby are key regions for global climate (Rhein
et al. 2011). Freshwater changes could potentially influence
this overturning system and thereby have a profound impact
on our climate (Koenigk et al. 2007; Rennermalm et al.
2007).
Fig. 2 Arctic summer sea ice
decline (Fetterer et al. 2016,
provided by the National
Snow and Ice Data Center
NSIDC, with permission). (a)
Arctic September (minimum)
sea ice extent in 2016 (white
area) compared to the median
ice edge for the period 1981
to 2010 (fuchsia line) and (b)
average monthly September
sea ice extent for the years
1979–2016, blue line: decline
rate of 13.2% per decade
relative to the 1981–2010
average
The Physical System of the Arctic Ocean and Subarctic Seas in a Changing Climate