Great Lakes Seasonal Summary 2008-09 english · Seasonal Summary for the Great Lakes - Winter 2008-2009 - 4 - General Overview of the 2008-2009 Season Observed temperatures for the

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Seasonal Summary for the Great Lakes - Winter 2008-2009 - 1 -

Produced by the North American Ice Service May 2009

Seasonal Summary

For the Great Lakes

Winter 2008-2009

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Table of Contents

General Overview of the 2008-2009 Season ......................................................................................... 4 Lake Superior......................................................................................................................................... 10 Lake Michigan........................................................................................................................................ 13 Lake Huron............................................................................................................................................. 16 Lake Erie................................................................................................................................................. 19 Lake Ontario........................................................................................................................................... 21

Table of Figures

Figure 1: Temperature anomaly, 01-31 December ............................................................................... 5 Figure 2: Temperature anomaly, 08-31 January................................................................................... 5 Figure 3: Temperature anomaly, 01-15 February ................................................................................. 6 Figure 4: Temperature anomaly, 15 February – 07 March................................................................... 6 Figure 5: Temperature anomaly, 08-31 March...................................................................................... 7 Figure 6: Temperature anomaly, 01 December - 30 April.................................................................... 7 Figure 7: Weekly ice coverage for the Great Lakes – 2008/09 ice season ........................................ 8 Figure 8: Historical ice coverage for the Great Lakes – 29 January, 2009 ........................................ 8 Figure 9: Historical ice coverage for the Great Lakes – 05 March, 2009 ........................................... 9 Figure 10: Historical total accumulated ice coverage, Great Lakes – 2008/09 ice season.............. 9 Figure 11: Weekly ice coverage for Lake Superior – 2008/09 season.............................................. 11 Figure 12: Historical ice coverage for Lake Superior – 12 February, 2009 ..................................... 11 Figure 13: Historical ice coverage for Lake Superior – 05 March, 2009 .......................................... 12 Figure 14: Historical total accumulated ice coverage, Lake Superior – 2008/09 ice season ........ 12 Figure 15: Weekly ice coverage for Lake Michigan – 2008/09 season............................................. 14 Figure 16: Historical ice coverage for Lake Michigan – 05 March, 2009 ......................................... 15 Figure 17: Historical total accumulated ice coverage, Lake Michigan – 2008/09 ice season........ 15 Figure 18: Weekly ice coverage for Lake Huron – 2008/09 season.................................................. 17 Figure 19: Historical ice coverage for Lake Huron – 05 March, 2009............................................... 17 Figure 20: Historical total accumulated ice coverage, Lake Huron – 2008/09 ice season............. 18 Figure 21: Weekly ice coverage for Lake Erie – 2008/09 season...................................................... 20 Figure 22: Historical total accumulated ice coverage, Lake Erie – 2008/09 ice season................. 20 Figure 23: Weekly ice coverage for Lake Ontario – 2008/09 season................................................ 22 Figure 24: Historical total accumulated ice coverage, Lake Ontario – 2008/09 ice season .......... 22 Figure 25: Departure from normal concentration and ice conditions – December 01st, 2008....... 23 Figure 26: Departure from normal concentration and ice conditions – December 08th, 2008....... 23 Figure 27: Departure from normal concentration and ice conditions – December 15th, 2008....... 23 Figure 28: Departure from normal concentration and ice conditions – December 22nd, 2008 ...... 24 Figure 29: Departure from normal concentration and ice conditions – December 29th, 2008....... 24 Figure 30: Departure from normal concentration and ice conditions – January 05th, 2009 .......... 24 Figure 31: Departure from normal concentration and ice conditions – January 12th, 2009 .......... 25 Figure 32: Departure from normal concentration and ice conditions – January 19th, 2009 .......... 25 Figure 33: Departure from normal concentration and ice conditions – January 26th, 2009 .......... 25 Figure 34: Departure from normal concentration and ice conditions – February 02nd, 2009 ........ 26 Figure 35: Departure from normal concentration and ice conditions – February 09th, 2009......... 26 Figure 36: Departure from normal concentration and ice conditions – February 16th, 2009......... 26

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Figure 37: Departure from normal concentration and ice conditions – February 23rd, 2009......... 27 Figure 38: Departure from normal concentration and ice conditions – March 02nd, 2009............. 27 Figure 39: Departure from normal concentration and ice conditions – March 09th, 2009.............. 27 Figure 40: Departure from normal concentration and ice conditions – March 16th, 2009.............. 28 Figure 41: Departure from normal concentration and ice conditions – March 23rd, 2009 ............. 28 Figure 42: Departure from normal concentration and ice conditions – March 30th, 2009.............. 28 Figure 43: Departure from normal concentration and ice conditions – April 06th, 2009................ 29 Figure 44: Departure from normal concentration and ice conditions – April 13th, 2009................ 29 Figure 45: Departure from normal concentration and ice conditions – April 20th, 2009................ 29 Figure 46: Departure from normal concentration and ice conditions – April 27th, 2009................ 30 Figure 47: Departure from normal concentration and ice conditions – May 04th, 2009 ................. 30

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General Overview of the 2008-2009 Season Observed temperatures for the month of November were generally above normal over the Great Lakes area. In December temperatures cooled to below normal values except near normal over the lower lakes (figure 1). January’s temperatures were below to well below normal over the lakes area except for the first week (figure 2). A return to above normal temperatures was observed during the first half of February (figure 3), only to give way to below normal temperatures during the last two weeks of the month and the first week of March (figure 4). The last three weeks of March were characterized by near normal temperatures except above normal over the lower lakes (figure 5). Near normal temperatures were the norm in April in most areas except above over the lower lakes. Overall during the winter season temperatures have been below normal except near normal over the lower lakes (figure 6). The ice development closely followed the temperature pattern described above. Ice formed in late November and early December in coastal areas and in shallow bays which is the norm. During December and through the first half of January the ice developed at a near normal pace and ice conditions at mid-January were close to normal (figure 7) . However the ice conditions changed dramatically in the second half of the month as very cold air invaded the lakes area (figure 2) allowing the ice to develop at a rapid pace. In fact, at the end of January, the ice cover in the lakes was the third highest extent on record, after 1977 and 1994 (figure 8). Little ice development was observed during the first half of February except in Lake Superior where both the ice cover and thicknesses increased significantly. The ice continued to develop during the following three weeks, especially during the first week of March. The ice cover in the lakes in general reached its maximum extent by the end of the first week of March which is about 10 days later than normal (figure 7). At that time the ice cover was much above normal and one of the highest on record (figure 9). Normally the maximum ice cover is attained during the last week of February. Break-up over the lakes started during the second week of March which is about 10 days late compared to the normal. Moderate to rapid ice melt was observed during the three weeks following the onset of break-up and at the end of March the ice cover was just slightly above normal (figure 7). April’s temperatures were in general close to normal in most areas so the break-up followed a near normal pattern. Overall this year’s ice coverage over the lakes was above normal and ranged in the top third since 1972 (figure 10).

The weekly ice analyses and the departure from normal ice concentration charts for the Great Lakes are included at the end of this document (figure 25 to figure 47).

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Figure 1: Temperature anomaly, 01-31 December

Figure 2: Temperature anomaly, 08-31 January

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Figure 3: Temperature anomaly, 01-15 February

Figure 4: Temperature anomaly, 15 February – 07 March

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Figure 5: Temperature anomaly, 08-31 March

Figure 6: Temperature anomaly, 01 December - 30 April

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Figure 7: Weekly ice coverage for the Great Lakes – 2008/09 ice season

Figure 8: Historical ice coverage for the Great Lakes – 29 January, 2009

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Figure 9: Historical ice coverage for the Great Lakes – 05 March, 2009

Figure 10: Historical total accumulated ice coverage, Great Lakes – 2008/09 ice season

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Lake Superior Colder than normal temperatures were generally reported in the last two weeks of November and the first two weeks of December. As a result the ice developed slightly earlier than normal. At mid-December ice conditions in Lake Superior were close to normal (figure 11). Ice conditions remained close to normal in the third week of December as temperatures remained on the cold side. However temperatures climbed to above normal during the last week of the month preventing any significant ice development. As a result at the end of 2008 the ice conditions were lighter than normal (figure 11). Despite somewhat colder than normal temperatures for most of the first half of January, ice conditions remained below normal. However just before mid-January temperatures dipped to much below normal values and remained so until the end of the month (figure 2). As a result the ice then developed at a rapid pace and at the end of January ice conditions were two to three weeks ahead of normal. In fact the ice coverage in Lake Superior went from around 12% to more than 50% during the second half of January (Figure 11). The first half of February was characterized by above normal temperatures over Lake Superior area (figure 3). Of note was the second week of the month where average temperatures were in excess of 5˚C above normal. Despite these mild temperatures, average temperatures were still cold enough to sustain significant ice development and growth but at a much slower pace than the previous two weeks. At mid-February, the ice was covering more than 70% of the lake which was the highest ice cover on record (for mid-February) since 1994 (figure 12). A return to below normal temperatures was observed in the second half of February. This allowed ice development to continue and ice conditions remained more severe than normal especially in the western section of the lake. At just above 80%, the ice cover at the end of February remained the highest since 1994. Below normal temperatures continued to predominate during the first half of March and ice continued to develop. At the end of the first week of March the ice cover in the lake was the third highest on record since 1970, after 1996 and 2003 (figure 13). Despite colder than normal temperatures during the second week the ice cover started to decrease, as average temperatures increased due to longer days. At mid-March, although lower than the previous week, the ice cover was much higher than normal and was the second highest since 1991. The second half of March was characterized by near to above normal temperatures over Lake Superior which allowed the ice to melt at a rapid pace. In fact at the end of March the ice over was about half of what it was two weeks before. Despite this rapid decline the ice cover, at that time, was still significantly above normal (figure 11). Near normal temperatures were reported during the first half of April which allowed the ice to melt at a moderate to rapid pace. As a result at mid-April the ice cover was close to normal (figure 11). Ice continued to melt as per normal during the second half of April and at the end of the month ice was only found in the bays along

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the north shore of the lake which is what we can normally expect at this time. All the ice in the bays melted during the second week of May. As for the total accumulated ice coverage in Lake Superior for the winter season, it was the fifth highest on record since 1972 (figure 14).

Figure 11: Weekly ice coverage for Lake Superior – 2008/09 season.

Figure 12: Historical ice coverage for Lake Superior – 12 February, 2009

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Figure 13: Historical ice coverage for Lake Superior – 05 March, 2009

Figure 14: Historical total accumulated ice coverage, Lake Superior – 2008/09 ice season

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Lake Michigan

Below normal temperatures were observed during late November through the first half of December resulting in early ice formation across many portions of Lake Michigan. Signs of new lake ice within Bays de Noc and along the southern portion of Green Bay were evident during the first week of December and by mid December the ice extent had just exceeded normal ice conditions (figure 15). At this time new and thin lake ice covered the southern portions of Green Bay and consolidated thin lake ice covered both Bays de Noc. The formation of new ice was also evident along Lake Michigans western coastline near Chicago. A sharp spike in colder temperatures during the third week of December resulted in significant ice growth across many of the ice prone areas including areas along the north shore, within the Straits of Mackinac, all of Green Bay, and along the western shoreline. During the last week of the month temperatures did moderate and climb above normal resulting in ice decay, however near normal ice conditions prevailed as we ended the year (figure 15). Observed temperatues across Lake Michigan were below to well below normal during most of January (figure 2). The below normal temperatures that occurred during the first half of the month resulted in near normal ice conditions across the majority of the lake by mid-month (figure 15). The thickest ice values were found in Bays de Noc, along the northern shoreline west of the Straits of Mackinac, and in southern portions of Green Bay. Just prior to mid month however, a severe and extensive cold snap captured the region (figure 2) allowing for significant ice development and growth. The well below normal temperatures stayed with the region through the end of the month when warmer temperatures finally began to filter into the area. The persistent cold temperatues during this period resulted in rapid ice development across the Lake creating an environment where ice conditions were two to three weeks ahead of normal (figure 15). At this time ice covered all shorelines within the Lake and consolidated medium and thick lake ice extended all throughout Green Bay and north and east of Beaver Island into the Straits of Mackinac. Also to note, a large coverage of medium and thin lake ice formed along the entire southern and eastern shoreline by the end of January which has not been seen for many years. The first half of February temperatures on average were above normal over Lake Michigan (figure 3) allowing most of the ice coverage along the western shore from Manitowoc southward to Chicago to melt by mid month. Interesting to note, during the second week of the month, Chicago reported temperatures in excess of 10C above normal. Winds out of the west during this period was also a major contributing factor for ice melt along the western shore. The ice would move off the coast into deeper, warmer water allowing for such melt to occur. Despite these milder than normal temperatures, termperatures were cold enough to sustain minimal ice growth and development across Green Bay, northern portions of the Lake, and along the eastern shore. At mid-February, ice conditions were back to near normal values (figure 15). A return to below normal temperatures was observed during the second half of February leading into March (figure 4). This allowed for significant ice

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development making ice condtions more severe than normal across the entire lake. Ice extent and thickness in early March (figure 15) exceeded normal values especially along the south-eastern and south-western shores. During the first week of March, maximum ice coverage values for Lake Michigan were obtained for the year (figure 15). The last time ice coverage values were at comparable levels was during the 2003 winter, followed by the 1994 winter (figure 16). After the first week of March, temperatues moderated a bit allowing normal temperatures to prevail for the remainder of the first half of March. During this time period all of the ice in the southern portion of the lake on both the eastern and western shores melted, ice coverage west and south of Beaver Island began depleting, and northern portions of Green Bay were seeing signs of ice breakup. By mid-March, average ice conditions prevailed (figure 15). The second half of the month, above normal temperatures were reported allowing for continual melt out and break up to occur. Both Bays de Noc , extreme eastern portions of Traverse Bay, and a small strip along the north shore just west of the Straits of Mackinac were the only areas in which consolidated ice remained at the end of March. At this point all of Green Bay was showing signs of fracture and decay. At the end of March the ice extent represented normal ice conditions across Lake Michigan (figure 15). Slightly below normal temperatures were observed during the first half of April, however with normal temperature values now above freezing for the day time high, ice conditions continued to deteriate. By mid-month ice was only evident in both Bays de Noc which was typical for this time of year. One week later all ice had melted and ice free conditions prevailed across Lake Michigan. The total accumulated ice coverage for the entire winter season for Lake Michigan is shown in figure 17.

Figure 15: Weekly ice coverage for Lake Michigan – 2008/09 season.

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Figure 16: Historical ice coverage for Lake Michigan – 05 March, 2009

Figure 17: Historical total accumulated ice coverage, Lake Michigan – 2008/09 ice season

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Lake Huron The second half of November and the first half of December were characterized by below normal temperatures over Lake Huron. Ice started to develop earlier than normal and at mid-December ice conditions were a week to 10 days ahead of the long term average (figure 18). Ice continued to develop in the third week of December but much warmer than normal temperatures during the last week of the month resulted in significant ice melt and destruction. As a result at the end of 2008 the ice coverage in Lake Huron was below normal (figure 18). Little ice development was observed in the first week of January as temperatures stayed in general close to normal. However, in the second week very cold temperatures invaded the area and ice developed at a rapid pace. At mid-January ice conditions were back to above normal (figure 18). The colder than normal temperatures that invaded the lakes area just before mid-January persisted through the rest of the month (figure 2) and allowed the ice to continue to develop at a rapid pace. At the end of January the ice coverage in Lake Huron was about 33% more than normal and the highest observed since 1994 (figure 18). Near normal temperatures were generally observed over Lake Huron during the first week of February but temperatures in excess of 5˚C above normal were the norm during the second week of the month( figure 3). As a result some of the ice melted and the ice cover at mid-February was lower than that at the beginning of the month (figure 18). Overall ice conditions at that time were close to normal. Ice growth and development resumed in the second half of February as temperatures dropped to below average values (figure 4). At the end of February, the ice cover was close to 50% more than normal (figure 18) and the second highest since 1996. Ice thicknesses, in general, were normal but thicker than normal in Georgian Bay. Below normal temperatures were generally observed during the first week of March which resulted in a significant increase in the ice cover. Normally at this time break-up is already under way. At the end of the first week of March the reported ice cover was still well above normal and remained the second highest since 1996 (figure 19). A return to above normal temperatures during the second week of March caused a rapid decline in the ice cover. While remaining above normal, the ice cover in Lake Huron at mid-March was approaching its normal value (figure 18). The shift to warmer temperatures that was observed in the second week of March continued into the last half of the month (figure 5) allowing the ice to melt at a moderate to rapid pace. So much so, that at the end of March the ice cover was below normal (figure 18). Near to below normal temperatures were the norm during the first half of April. The drifting ice in the northern half of the lake and in Georgian Bay all melted during the first and second week of the month, respectively. At mid-month the only ice remaining was found in the North Channel and in bays along the northeast shore of Georgian Bay. With the help of above normal temperatures during the last two weeks of April, all the ice in Georgian bay and in the North Channel melted by month’s end.

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The break-up followed a near normal pattern despite heavier than normal ice conditions for most of the season. The total accumulated ice coverage for the winter 2008-2009 for Lake Huron is shown in figure 20.

Figure 18: Weekly ice coverage for Lake Huron – 2008/09 season

Figure 19: Historical ice coverage for Lake Huron – 05 March, 2009

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Figure 20: Historical total accumulated ice coverage, Lake Huron – 2008/09 ice season

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Lake Erie Temperatures during the last two weeks of November and the first two of December were below normal in general. At mid-December the Western Basin and Lake St Clair were covered with new and thin lake ice which is a week earlier than normal. Ice continued to develop at a rapid pace during the third week of December but milder conditions during the last week of the month resulted in significant ice melt and destruction. Ice coverage in Lake Erie, which was above normal at the end of the third week of December, was well below normal at the end of 2008 (figure 21). Near normal temperatures were generally reported during the first week of January followed by colder to much colder than normal during the second week. As a result rapid ice development was observed especially during the second week. At mid-January ice conditions were two weeks ahead of normal (figure 21). Below to much below normal temperatures prevailed in the second half of January (figure 2) and as a result Lake Erie was almost entirely ice covered at the end of the third week of the month (figure 21). Such an ice cover is normally seen two weeks later. Near normal temperatures prevailed during the first week of February followed by much above normal temperatures during the second week (figure 3). As a result no significant ice development was observed in Lake Erie during the period. In fact a slight decrease in the ice cover was noticed. The ice thicknesses did increase in the eastern section of the lake but it was mainly caused by ice pressure rather than cold temperatures. At mid-February Lake Erie was about 80% ice covered which is close to normal (figure 21). Typically break-up in Lake Erie starts during the second half of February but thanks to colder than normal temperatures the onset of break-up was delayed and ice continued to form and thicken throughout the month. As a result the ice cover in Lake Erie was well above normal at the end of February (figure 21). Near to below normal temperatures were generally reported during the first week of March allowing the ice to develop further. Normally at this time break-up would be well under way. At the end of the first week of March, the ice cover in Lake Erie was close to 100 percent when it would normally be near 50 percent (figure 21). Temperatures warmed up significantly during the second week of the month allowing the ice to melt at a rapid pace. At mid-March the ice cover in the lake, while remaining above normal, was leaning towards its normal value. Above normal temperatures continued during the last two weeks of March. This, combined with the normal increase in average temperatures, resulted in rapid ice melt and at the end of March the ice cover was close to normal (figure 21).

Near normal temperatures prevailed during the first half of April. Most of the ice in the eastern section of the lake melted during the first week of the month. The little ice that survived through the first week of April lingered along the coast near Buffalo for another week before it melted. Overall the ice coverage in Lake Erie over the winter season has been more extensive than normal (figure 22).

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Figure 21: Weekly ice coverage for Lake Erie – 2008/09 season

Figure 22: Historical total accumulated ice coverage, Lake Erie – 2008/09 ice season

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Lake Ontario Below normal temperatures generally prevailed in Lake Ontario from mid-November to mid-December. As a result the ice started to form in Bay of Quinte just before mid-December which is about a week earlier than normal. The third week of December was colder than normal which permitted the development of a narrow band of ice along the northern shore of the lake. This band melted during the last week of the month when temperatures rose to above to well above normal values. At the end of December Bay of Quinte was ice covered but the rest of Lake Ontario was open water to ice free which is a near normal situation.

The first week of January was characterized by near normal temperature and the ice developed at a normal pace. Very cold temperatures invaded the area during the second week of the month which allowed the ice to develop at a rapid pace. At mid-January more ice than normal was present in the northeast section of the lake. Below normal temperatures continued to predominate during the second half of January (figure 2). Despite this, the ice coverage at the end of January remained close to normal (figure 23). The ice, however, was thicker than normal.

Temperatures were near normal during the first week of February but climbed

to much above normal during the second week (figure 3). As a result no significant ice development occurred during the first half of February. Near normal temperatures were generally reported in the second half of February. Break-up usually sets in during the second half of February and such was the case this year as a decrease in the ice cover was observed during that period. At the end of February the ice cover was close to normal (figure 23).

Slightly above normal temperatures were generally observed in the first two

weeks of March. As a result some of the drifting ice in the northeast section of the lake melted during that time period. At mid-March the only ice remaining was a narrow band of thick lake ice along the northeast shore. This was a near normal situation. The western section on the Seaway fractured just before mid-month, a week to 10 days earlier than normal. Above normal temperatures prevailed during the second half of March and as a result all of the drifting ice in the northeast section of the lake melted during the third week of March. Bay of Quinte started to fracture during the third week of March and was mostly open water at the end of the month. At that time patchy areas of loose ice were found in the western section of the river.

The little ice that was present in Bay of Quinte and in the western section of the

St Lawrence River at the beginning of April melted during the first few days of the month. Break-up was close to normal. The total accumulated ice coverage for Lake Ontario for the winter season 2008-2009 was less than normal (figure 24).

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Figure 23: Weekly ice coverage for Lake Ontario – 2008/09 season

Figure 24: Historical total accumulated ice coverage, Lake Ontario – 2008/09 ice season

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Figure 25: Departure from normal concentration and ice conditions – December 01st, 2008

Figure 26: Departure from normal concentration and ice conditions – December 08th, 2008


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Figure 28: Departure from normal concentration and ice conditions – December 22nd, 2008


Figure 30: Departure from normal concentration and ice conditions – January 05th, 2009

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Figure 34: Departure from normal concentration and ice conditions – February 02nd, 2009

Figure 35: Departure from normal concentration and ice conditions – February 09th, 2009

Figure 36: Departure from normal concentration and ice conditions – February 16th, 2009

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Figure 37: Departure from normal concentration and ice conditions – February 23rd, 2009

Figure 38: Departure from normal concentration and ice conditions – March 02nd, 2009

Figure 39: Departure from normal concentration and ice conditions – March 09th, 2009

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Figure 41: Departure from normal concentration and ice conditions – March 23rd, 2009


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Figure 43: Departure from normal concentration and ice conditions – April 06th, 2009



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Figure 47: Departure from normal concentration and ice conditions – May 04th, 2009

Documents

Great Lakes Seasonal Summary 2008-09 english · Seasonal Summary for the Great Lakes - Winter 2008-2009 - 4 - General Overview of the 2008-2009 Season Observed temperatures for the