Influence of Meltwater from Labrador Sea ice and icebergs transported
via Flemish Cap on the long-term North Atlantic Cold Anomaly
Abstract
The long-term North Atlantic Cold Anomaly (Cold Blob) was largely the
consequence of three major episodes of low sea surface temperature (SST)
in the subpolar North Atlantic in 1972-74, 1984-85 and 1991-94. Each of
these episodes correlated with unusually low SST at Flemish Cap (a
subsurface island of the Canadian continental shelf 600km east of
Newfoundland) and with periods of high sea-ice cover over the deep basin
of the Labrador Sea a year earlier. These cold periods at Flemish Cap
and the Cold Blob were associated with the advance of sea-ice and
icebergs to Flemish Cap, high iceberg counts off the coast of
Newfoundland and the appearance of icebergs along the path of the North
Atlantic Current (NAC) east of Flemish Cap. Studies of SST anomalies
provided evidence for surface connections between Flemish Cap and the CB
which utilize part of the NAC pathway. We propose that in the cold
periods, residual meltwater from sea-ice and icebergs conveyed in the
Labrador Current to Flemish Cap was relayed via the NAC to the subpolar
North Atlantic to form the Cold Blob. After 1995, anomalous ice
expansion in the Labrador Sea basin greatly diminished, sea-ice and
icebergs did not reach Flemish Cap and cold meltwater was no longer
transmitted to the subpolar North Atlantic to sustain the Cold Blob.
This improved understanding of 20th century meltwater pathways in the
North Atlantic may relate to changes in the Atlantic Meridional
Overturning Circulation and associated impacts on regional climate in
the 21st century.