MURSYS - North Sea and Baltic Sea - Report 1 2008





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MURSYS - North Sea and Baltic Sea - Report 1 2008

   
 
 

Marine Environmental Reporting System - Abstract - Reporting Period: 1 January - 30 June 2008

North Sea

Weather

Early January 2008 saw mild weather with monthly mean temperatures of about 5 °C, which was 3 - 4 K above average. The recorded 80 -  mm of precipitation was higher than normal and exceeded monthly means by up to 80 %. With only 15 - 25 hours of sunshine, less than half of the mean values was reached. Strong winds gusting up to gale-force occurred repeatedly in the course of the month.
February remained mild, with monthly mean temperatures of 5 °C exceeding the mean values by about 3 - 4 K. Between 7 and 21 February, there was no measurable precipitation due to a persistent high-pressure system, and only copious precipitation of 40 bis 50 mm toward the end of the month caused monthly mean values to be exceeded by up to 30 %. Also the duration of sunshine, at 70 - 90 hours, exceeded the mean values by up to 30 %. Winds were weak under the influence of high pressure, while westerly weather conditions at the beginning and end of the month often brought gale-force winds.
Although monthly mean temperatures in March reached 5 - 6 °C, which was 1 - 2 K above the long-term means, there also occurred cold spells with snow showers. This month's high precipitation of 70 - 100 mm exceeded the mean values by about 50 - 100 %. Nevertheless, the 100 - 140 hours of sunshine in March were about normal and even exceeded mean values locally by up to 20 %. This month saw very windy, occasionally even stormy weather.
In April, monthly mean temperatures of close to 8 °C were 1 - 2 K above the reference values. This month was too dry in most areas, with precipitation as low as 20 - 40 mm, which was about 30 % below normal. The duration of sunshine, at 170 - 220 hours, was up to 25 % above average. No storms occurred during this month.
In the sunny and largely dry month of May, monthly mean temperatures reached 13 - 15 °C, which was 2 - 3 K above average. Precipitation, at up to 20 mm, reached only 10 - 30 % of normal values. 300 to 360 hours of sunshine were recorded, which was 40 - 60 above the reference values. Weak winds prevailed.
June was too warm and dry. Monthly mean temperatures ranged between 15 and 17 °C, which was 1 - 2 K above average. At 20 - 40 mm, only 50 % of normal precipitation was recorded in most areas, with the exception of East Friesland where 45 - 60 mm of rain fell, corresponding to about 65 - 85 % of normal values. The duration of sunshine, at 240 - 305 hours, exceeded the monthly means by 15 - 30 %.

Water temperatures

The monthly mean value of sea surface temperatures (SST) is compared to the so-called climatological value (1971 - 1993). The ranking among the highest SST monthly mean values since 1971 is given in brackets.

The monthly mean SST of the North Sea in January 2008 was 7.4 °C, which was 0.9 K above the climatological value (rank 6 among the highest mean January SST since 1971).
The February mean temperature of 6.9 °Cexceeded the climatological mean by 1.2 K (rank 6).
In March , the mean SST of 6.7 °C was 1.0 K above the climatological value (also rank 6)
SST in April reached 7.2 °C, exceeding the climatological mean by 0.5 K (rank 9).
In May, SST on average rose to 10.8 °C, which was 1.7 K above the climatological mean (rank 2).
SST in June rose to 13.2 °C and exceeded the climatological value by 1.2 K (rank 5).

Surface runoff

In the first half of 2008, surface runoff of the river Elbe (Neu-Darchow gauge station) in January and March was slightly above the mean values of the period from 1926 to 2004, and in February and April runoff was clearly higher. Runoff was slightly below the mean values in May, and far below these values in June.
Runoff of the river Weser (Intschede gauge station) from January to April was clearly above the runoff means of the 1951 - 2004 reference period. In May, runoff was on the order of the reference mean, and in June it was below it.
Runoff of the Ems (Versen gauge station) exceeded the reference means of the period 1951 - 2004 clearly in January and March, and slightly in February and April. In May, runoff was slightly below the reference value, and in June it was on the order of the reference value.
Surface runoff of the Rhine (Rees gauge station) in May and June was on the order of the values of the 1931 - 2004 reference series. In March and April, values were clearly higher, in January they were slightly higher, and in February clearly lower than the reference means.

Ice conditions

The ice winter of 2007/08 led to a very weak ice season on the German coasts. The North Sea coast remained ice free, with the exception of two days (05./06.01.08) with weak ice formation in the harbour of Tönning.

Baltic Sea

Weather

January 2008 was even milder than the preceding month, with monthly mean temperatures of 3 - 4 °C in the Baltic Sea region, which was 3 - 4 K above the mean values of the 1961 - 1990 reference period. With the exception of Fehmarn and Rügen, about 45 - 70 mm precipitation was recorded, exceeding the mean values by up to 30 %, in easterly regions by as much as 60 - 70 %. Winds were occasionally strong and reached gale force in gusts.
February was the mildest and sunniest month of this winter, with normal monthly means of zero to 1 °C exceeded by 4 - 5 K. There were no days with ice. Precipitation ranged between 20 and just under 40 mm, which was 30 bis 40 % below average on the Baltic Sea islands, and in other areas corresponded to the mean values or exceeded them locally (Boltenhagen, Ueckermünde) by up to 60 %. The duration of sunshine, at 80 - 96 hours, was up to 50 % above the mean values; east of Rügen and in the area of Kleines Haff, the weather was less sunny. The highest wind speeds, often reached in hurricane-force gusts, were recorded around 22 February.
March brought more snow than the entire winter of 2007/2008, which was 3 - 4 K too warm. Nevertheless, its monthly mean temperatures of 4 - 5 °C were about 2 K above the long-term reference values. The 50 - 60 mm monthly precipitation recorded along the coasts exceeded the mean values by 40 - 70 % (10 % on the Baltic Sea islands, with about 37 mm precipitation). A complete snow cover was recorded on maximally six days. The 120 - 150 hours of sunshine recorded during this month nevertheless exceeded the mean values by up to 40 % (exception: Kleines Haff, with only 87 hours). Strong winds reaching hurricane force in gusts occurred in early and mid-March.
Although April started with low temperatures, monthly means still reached 7 - 8 °C, which was 1 - 2 K too warm. Precipitation in the western Baltic Sea region was 40 - 50 mm, up to 20 % above the long-term means; east of the Darss peninsula, at 70 - 100 mm, it was almost twice as high. The 180 - 210 hours of sunshine recorded during this month exceeded the mean values by up to 20 %. East of Rügen, the sun shone only on 140 - 150 hours, which was 15 % below normal.
The dry and sunny month of May, with mean temperatures between 12 and 13.5 °C, generally was 1 - 2.5 K too warm. In most areas, only 5 - 20 mm rain fell in this month, which was less than half, in some areas only 10 - 20 %, of the monthly reference means (exception: Cape Arkona, at 37 mm, almost corresponded to the mean values). The 350 - 400 hours of sunshine recorded in May set a new record, with mean values exceeded by 50 bis 60 %. Strong winds occurred in the last decade of the month.
June, with monthly mean temperatures between 15 and 17 °C, was about 1 K too warm. After a lengthy dry spell, some 20 - 40 mm rain fell in the course of the month, which was 30 - 85 % of the monthly means. With 270 - 315 hours of sunshine, the monthly means were exceeded by 15 - 20 %. The wind freshened up temporarily and reached gale force in gusts.

Water temperatures

In January 2008, mean water temperatures in the Baltic coastal waters of Mecklenburg-Vorpommern reached 4.1 °C off Warnemünde and 2.1 °C off Koserow (at 3 m m depth), which was 1.3 K above the values of the 1997 - 2007 reference series at Warnemünde and on the order of the 1998 - 2007 reference series at Koserow.
In February, the mean water temperature at Warnemünde was 4.0 °C, which was 1.5 K above the reference series. The mean water temperature of 3.0 °C recorded at Koserow exceeded the reference value by 1.4 K.
Also in March, mean temperatures remained above the values of the reference series: by 1.3 K off Warnemünde, at 4.7 °C, and by 1.6 K off Koserow, at 4.3 °C.
In April, 6.8 °C was measured at Warnemünde, and 6.4 °C at Koserow, which was 1 K and 0.3 K, respectively, above the values of the reference series.
In May, with mean water temperatures of 11.2 °C at Warnemünde and 13.5 °C at Koserow, the reference values were exceeded by 0.7 K and 1.8 K, respectively.
Mean water temperatures in June reached 15.7 °C off Warnemünde, and 16.6 °C off Koserow, exceeding the reference values by 0.8 K and 0.9 K, respectively.

Water levels

Monthly mean water levels on the Baltic coasts of Schleswig-Holstein and Mecklenburg-Vorpommern in January 2008, measured at Travemünde and Warnemünde, were 3 cm below the values of the reference series (Schleswig-Holstein: 1996 - 2005, Mecklenburg-Vorpommern:1997 - 2006). Recorded extrema were the minimum level of 400 cm recorded at the Flensburg gauge station on 26.01, and the maximum level of 582 cm recorded in Flensburg and Koserow on 03.01 and 27.01, respectively.
In February, mean water levels exceeded the reference levels by 3 cm at Travemünde and 2 cm at Warnemünde. The lowest water level (408 cm) was recorded at Flensburg on 01.02, the highest level (580 cm) at Koserow on 15.02.
Monthly means in March again exceeded the values of the reference series, in Schleswig-Holstein (Travemünde) by 25 cm, and in Mecklenburg-Vorpommern (Koserow) by 27 cm. Both the minimum value of 420 cm and the maximum value of 640 cm were recorded at the Wismar gauge station on 06.03 and 22.03, respectively.
Mean water levels in April exceeded the reference values by 11 cm in Schleswig-Holstein (Travemünde), and by 6 cm in Mecklenburg-Vorpommern (Warnemünde). The minimum value of 471 cm was recorded at Flensburg on 26.04, the maximum value of 553 cm at Lübeck on 08.04.
In May, the monthly mean water levels in Schleswig-Holstein (Kiel) were 7 cm higher than the long-term means, in Mecklenburg-Vorpommern (Koserow) they were 4 cm lower. The lowest level this month was 473 cm recorded both at Wismar and Kiel on 11.05., and the highest level was 581 cm measured in Eckernförde on 13.05.
Mean water levels in June were below the values of the reference series, in Schleswig-Holstein by 4 cm (Travemünde), and in Mecklenburg-Vorpommern by 12 cm (Koserow). At the Flensburg gauge station, both the lowest and the highest water levels of 417 cm and 538 cm were recorded on 23.06. and 03.06, respectively.

Surface runoff

In the first half of 2008, runoff of the river Odra (Hohensaaten-Finow gauge station) exceeded the runoff means of the 1941 - 2004 reference series only in February. In January and from March to June, runoff was below the long-term means.

Ice conditions

The ice winter of 2007/2008 will enter the statistics (since 1720) as the mildest winter in terms of ice extent. The maximum ice cover during the ice season of 2007/2008 was 49.000 km², recorded on 24 March 2008; it was even smaller than the former record low of 52.000 km² recorded in 1989.
In the Bay of Bothnia, which freezes over completely each winter, a complete ice cover was reached as late as 23 March this year, attributable solely to the cold weather around Easter.
With regard to shipping, the mild winter meant exceptionally low icebreaker deployment. In the Gulf of Finland, icebreakers were needed on just one day, which is unprecedented in this area.
Because of unusually mild weather in October 2007, ice formation in the northern Bay of Bothnia and eastern part of the Gulf of Finland set in as late as mid-November, one to two weeks later than normal. Also during the mild month of December, there was no major growth of ice. It was not until early January that cold weather caused ice formation to continue along the coasts of the northern Baltic Sea, with some new ice forming also in the shallow, sheltered coastal waters of Mecklenburg-Vorpommern. However, temperatures went up again after about one week, slowing down ice formation. Consequently, the extent of ice cover on the Baltic Sea lagged several weeks behind its average development. Another cold spell setting in as late as mid-February led to increased ice formation. In early and late March, intensive ice formation continued, causing the maximum ice cover to be reached on 24.03; also the Bay of Bothnia temporarily had a complete ice cover. A mild spell in early April caused a retreat of ice in the northern Baltic Sea region. On 15 May, the Bay of Bothnia was free of ice. The ice winter in this area thus was almost five weeks shorter than normal.

The ice winter of 2007/08 led to a very weak ice season on the German coasts. The accumulated areal ice volume computed for the Baltic Sea was 0.01 m. Although the total volume of ice was larger than last winter, ice formation was limited to the shallow, sheltered coastal waters. Also this winter, the open sea remained ice-free.

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