Arctic Ocean warming and its consequences for the Denmark Strait overflow

Abstract

Two anomalously warm inflow pulses into the Atlantic Water Layer of the Arctic Ocean have occurred since the late 1980s. As a consequence temperatures of the Arctic basins at 200–800 m depth have increased considerably in comparison to earlier decades. The warm inflow pulses also had a low density. Owing to the decadal time scale of the circulation in the Atlantic Water Layer large pools of anomalously light water have thereby formed in the Arctic Ocean. These will slowly drain back south into the Nordic Seas. We submit that they will be able to influence the overflows into the Atlantic across the Greenland‐Scotland ridges. The Atlantic meridional overturning is fed by these overflows. Our model experiments indicate that the low‐density anomalies from the Arctic Ocean may be able to reduce the Denmark Strait overflow 15–25 years after the entrance of the original signal through Fram Strait into the Arctic Ocean. The actual size of the reduction depends on the exact path and speed of the anomalies inside the Arctic proper and on local processes in the Arctic Ocean and the Nordic Sea.

Changes in the properties and distribution of the intermediate and deep waters in the Fram Strait

“…Changes in temperature and salinity (if they do not compensate each other in density) will affect the pressure gradients that influence the exchanges between different basins (e.g., Østerhus and Gammelsrød, 1999;Karcher et al 2011). What the circulation will look like if all of the deep waters end up having the same properties, as the AODW, is an open question.…”

A Synthesis of Exchanges Through the Main Oceanic Gateways to the Arctic Ocean

“…Model studies (e.g., Häkkinen and Geiger, 2000;Karcher et al, 2003) (Schauer et al, 2008;Skagseth et al, 2008). Karcher et al (2008Karcher et al ( , 2011 point out that, both in observations and model results, the anomalously warm inflows were also characterized by negative density anomalies. Karcher et al (2011) …”

Recent advances in understanding the Arctic climate system state and change from a sea ice perspective: a review

“…These are expected to slowly drain back south into the Nordic Seas (Karcher et al, 2011), with the anticipated effect of a reduced Denmark Strait overflow into the North Atlantic Ocean.…”