The database managers are not liable for ensuring the accuracy of the original data; this is the responsibility of individual data contributors. Some basic quality control checks were performed on contributed data and, in some cases, corrections were made; however, we recommend that users of the database screen the data for inconsistencies that might indicate errors.

May 2020

Corrected Lake Suwa Japan data with lake code ARAI1 were added back into the database and six new years (2008 - 2013) of Tornio River (EK26) data were also added.

Note: In Sharma et al. (2016, pg 6), the authors make the following statement about the Lake Suwa data:

"Unfortunately, there are missing data in the midyears of the time series (1505–1515) and more importantly, data from 1682–83 to 1922–23 are considered unreliable for analysis ice cover freeze dates. In those middle years, various changes in the calendar confused the record, ice cover dates often were indicated as approximate or were not provided even though the lake did freeze over, the group making the observations varied, and Omiwatari date or even the Omiwartari ceremony often were substituted for the ice cover date. We eliminated all data from 1682–1923 from the analyses to reduce the uncertainty in dates of ice freeze. However, the ice-freeze date between 1443–1682 and 1924–2018, in addition to the presence or absence of lake freeze from 1443–2018 are considered to be very reliable. For years when more than one data source was available (1897–1993), we numerically compared the values. In almost all years they were the same and if not, the standard deviation between the values between 1944 and 1996 was 2.65. When they were not the same, we used Arakawa over the Suwa Meteorological Observatory and Yatsurugi Shrine from 1443 to 1953; from 1953 to 1993 we used the Suwa Meteorological Observatory over the Yatsurugi Shrine, and from 1994 to 2018 we used Yatsurugi Shrine. There were 3 exceptions to these choices (1950 we used the Suwa Meteorological Observatory; 1952 and 1976 where we used information from Tadashi Arai). Ice freeze dates occur before and after January 1st, therefore we converted dates to day of year, using a zero to represent the calendar day January 1st."

September 2015

The Lake Suwa Japan data with lake code ARAI1 were temporarily removed from the database due to an error found in the calendar correction for the data.

January 2014

An update was made to the database to address discrepancies in the St. Regis Lower lake (KMS16) data noted by C. Stager of Paul Smiths College. He found several data to be conflicting with the records he had found at the college library. The discrepancies have been addressed by adding comments to KMS16 and adding a new record with lakecode: CS1. Stager feels strongly that the older data (before 1970) may be for a different lake because the college did not exist at the time. There are also some discrepancies in single dates after 1970.

In addition, the North Temperate Lakes Long Term Ecology Research (NTL-LTER) sent updates for ten lakes in the NTL region for 2010 to 2013: Allequash Lake (JJM1), Big Muskellunge Lake (JJM2), Crystal Bog (JJM3), Crystal Lake (JJM4), Lake Mendota (DMR1), Lake Monona (DMR2), Lake Wingra (JJM18), Sparkling Lake (JJM6), Trout Bog (JJM7), and Trout Lake (JJM8).

January 2012

Notice: 22 September 2015 - The Lake Suwa Japan data with lake code ARAI1 have been temporarily removed from the database due to an error found in the calendar correction for the data. The data providers are working on a correction but there is no timeline for completion.

A calendar correction was made to the Lake Suwa, Japan data. The LIAG team had erroneously assumed that the translation from the ancient Japanese calendar to Gregorian dates set the first month of the year to February and not January. However, when they consulted the original datasheets in Japan, the first month was indeed January. Therefore, the LIAG team introduced a negative 30 day correction to the Lake Suwa data before 1872 to fix this. Change applied 1 February 2012.

NSIDC has received inquiries from users asking about the location of Bigwood Lake (WRS214). Users should note that Bigwood Lake (WRS214) in the NSIDC database refers to the small lake near Sioux Lookout, Ontario and not the Bigwood Lake near Sudbury.

February 2007

The following changes were made to the NSIDC database for Detroit Lake, MN (MINN2):

New data:

• "Ice on" dates and ice duration for start years 1899, 1902, 1903, 1908, 1909, and 1980 - 2001.
• "Ice off" dates for start years 2004, 2005.

Changed data:

• "Ice on" date changed from October 28, 1913 to December 8, 1913.
• Ice duration for 1913-1914 changed from 177 days to 136 days.
• "Ice off" date changed from May 19, 1908 to April 19, 1908 for the 1907-1908 ice season.

Note that discrepancies between the NSIDC database and other sources may exist.

In February 2007, a user noted discrepancies between the Detroit Lake, MN data in our NSIDC database and the Becker County Record (Detroit Lakes Newspaper) from April of 2002. David Balsiger looked into this and noted that some discrepancies range from one to five days and some are of even greater magnitude. Pete Boulay (Assistant State Climatologist for the Minnesota State Climatology Office, Department of Natural Resources - Division of Waters) responded with the following:

"Determining ice-out is far from an exact science. Depending on what definition of "ice-out" is used, the dates can vary considerably. Some people choose being able to get from Point "A" to Point "B" and some wait until every last ice crystal is melted.

Every effort is made to use the same source for ice out from year to year. Individuals that live on the lake have tended to be very good sources. Their view of the lake will not be flawless: (they may have limited view.) I have noted that lake residents will often call friends across the lake to verify their date. Newspapers can vary with accounts. Small newspapers may have staff that changes fairly often. One editor may have a different idea what "ice out" means from another so this can be difficult."

July 2006

NSIDC received corrections from David Balsiger (University of Wisconsin-Madison). The corrections have been fixed in the NSIDC database and include the following:

• The latitude and longitude coordinates for Lake Geneva (JJM27) were changed to 42.57 (latitude) and -88.50 (longitude).
• Coordinates for Lake Baikal (NG1) have been changed to 51.85 (latitude) and 104.87 (longitude).
• Corrections were made for Lake Baikal (NG1) for "ice off" dates in 1981-82, 1982-83, and 1991-92 through 1995-96. "Ice on" dates were updated for 1994-95.
• These errors were in the original data submitted to our data providers. Correct dates were obtained from the Minnesota state climatologist and confirmed by the original contributor.