Sea temperatures
West Greenland Current temperatures remain high
- This year, Mads Hvid Ribergaard once again performed his investigations from the Danish navy's patrol cutter Tulugaq.
08.10.11
In close collaboration with Pinngortitaleriffik/Greenland Institute of Natural Resources, the Center for Ocean and Ice at the Danish Meteorological Institute (DMI) has been investigating oceanographic conditions along West Greenland for some years from Cape Farewell in the south to Sisimiut in the north. The purpose is to investigate marine climate variations in the sea area.
Pinngortitaleriffik uses these data in scientific work concerning the relation between variations in the marine environment and the sizes of the most important Greenlandic fish stocks. This work constitutes an important factor in the institute's fish stock assessments. In addition, time series of up to 60 years play an important part in the general understanding of North Atlantic Ocean currents and their natural variations.
The most pronounced feature of the 2011 measurements is that very high salinities and corresponding high temperatures are still being observed in deep waters west of the shelf/Fyllas Banke. Thus, the Irminger Current is continuously providing large amounts of heat to South West Greenland waters. This affects fish stocks, but it also affects Greenlandic outlet glaciers. Recent research indicates that several outlet glaciers are strongly affected by warm underlying water masses and therefore melt more rapidly.
Temperatures as well as salinities measured at the top of Fyllas Banke were higher than normal (Figure 1). In contrast, the surface water west of the banks to the north was colder than normal, probably reflecting a remnant of winter's direct effect on Greenlandic waters, and it will likely return to its normal level in the course of summer. At greater depths west of the banks, very high salinities and corresponding high temperatures were generally observed (Figure 2), which has been the case for several years.
- Figure 1. Mid-June sea temperatures and salinities across Fyllas Banke (0-40 m) in the period 1950-2011. The 3-year running mean is shown in red. The temperature time series has been extended using data processed by Jens Smed for the period 1876-1975, which cover a larger area, but which show a surprisingly good agreement in the overlapping period.
- Figure 2. Mid-June sea temperatures and salinities west of Fyllas Banke at depth 400−600 m in the period 1950-2011. The 3-year running mean is shown in red.
In order to understand the temperature variations, one must take a wider approach. The marine environment across the South East and West Greenland fish banks is controlled to a large extent by external water masses from both polar and temperate areas (Figure 3):
- Red IC: Warm, salty Irminger water. It is transported to the area by the Irminger Current, which branches off the North Atlantic Current.
- Blue EGC: Cold Polar Water of low salinity deriving from the Arctic Ocean. It is carried south together with large amounts of sea ice by the East Greenland Current.
These two water masses meet for the first time in the northern Irminger Sea and Denmark Strait, after which they move south side by side along the east coast of Greenland.
Having passed Cape Farewell, the Irminger water dives below the Polar Water.
On the way, the water masses are mixed and, hence, hydrographical conditions across the South East and West Greenland fish banks are determined by the balance of power between the Irminger Current and the East Greenland Current. Thus, changes in North Atlantic circulation will greatly influence sea temperatures.
- Figure 3: Schematic representation of surface currents around Greenland. The North Atlantic current is shown in red. The branch extending to Greenland is called the Irminger Current (IC). The dark blue arrow shows the East Greenland Current (EGC) and the West Greenland Current (WGC) is shown in purple. Each year, DMI carries out oceanographic measurements along West Greenland at 30 fixed positions along six cross sections shown in orange. Until now, the 4 southernmost legs have been observed.