Liquid export of Arctic freshwater components through the Fram Strait 1998–2011 1Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany
30 Jan 2013
2Norwegian Polar Institute, Tromsø, Norway
3The University Centre in Svalbard, Longyearbyen, Norway
4National Oceanography Centre, Southampton, UK
Received: 23 Jul 2012 – Published in Ocean Sci. Discuss.: 14 Aug 2012Abstract. We estimated the magnitude and composition of southward liquid freshwater
transports in the East Greenland Current
near 79° N in the Western Fram Strait between 1998 and 2011.
Previous studies have found this region
to be an important pathway for liquid freshwater export from the
Arctic Ocean to the Nordic Seas and the North Atlantic subpolar gyre.
Revised: 22 Dec 2012 – Accepted: 10 Jan 2013 – Published: 30 Jan 2013
Our transport estimates are based on six hydrographic surveys between June
and September and concurrent data from moored current meters. We combined
concentrations of liquid freshwater, meteoric water (river water and
precipitation), sea ice melt and brine from sea ice formation, and Pacific
Water, presented in Dodd et al. (2012), with volume transport estimates from an
inverse model. The average of the monthly snapshots of southward liquid
freshwater transports between 10.6° W and 4° E is
100 ± 23 mSv (3160 ± 730 km3 yr−1), relative to a
salinity of 34.9. This liquid freshwater transport consists of about 130%
water from rivers and precipitation (meteoric water), 30% freshwater from
the Pacific, and −60% (freshwater deficit) due to a mixture of sea ice
melt and brine from sea ice formation.
Pacific Water transports showed the highest variation in time,
effectively vanishing in some of the surveys.
Comparison of our results to the literature indicates that this was
due to atmospherically driven variability in the advection of Pacific Water
along different pathways through the Arctic Ocean.
Variations in most liquid freshwater component transports appear to
have been most strongly influenced by changes in the
advection of these water masses to the Fram Strait.
However, the local dynamics represented by the volume transports influenced
the liquid freshwater component transports in individual years, in particular
those of sea ice melt and brine from sea ice formation.
Our results show a similar ratio of the transports of meteoric water and
net sea ice melt as previous studies. However, we observed a significant
increase in this ratio between the surveys in 1998 and in 2009.
This can be attributed to higher concentrations of sea ice melt in 2009 that
may have been due to enhanced advection of freshwater from the Beaufort Gyre to
the Fram Strait.
Known trends and variability in the Arctic liquid freshwater inflow
from rivers are not likely to have had a significant influence on
the variation of liquid freshwater component transports between our surveys.
On the other hand, known freshwater inflow variability from the Pacific could
have caused some of the variation we observed in the Fram Strait.
The apparent absence of a trend in southward liquid freshwater transports
through the Fram Strait and recent evidence of an increase in liquid
freshwater storage in the Arctic Ocean raise the question: how fast will the
accumulated liquid freshwater be exported from the Arctic Ocean to the deep
water formation regions in the North Atlantic and will an increased export
occur through the Fram Strait.
Citation: Rabe, B., Dodd, P. A., Hansen, E., Falck, E., Schauer, U., Mackensen, A., Beszczynska-Möller, A., Kattner, G., Rohling, E. J., and Cox, K.: Liquid export of Arctic freshwater components through the Fram Strait 1998–2011, Ocean Sci., 9, 91-109, doi:10.5194/os-9-91-2013, 2013.