Hubbard Brook Experimental Forest: Mirror Lake Ice Cover 1968 - present
Hubbard Brook Experimental Forest: Mirror Lake Ice Cover 1968 - present
Gene Likens
Cary Institute of Ecosystem Studies
2801 Sharon Turnpike
Millbrook, NY 12545
Mirror Lake is located within the Hubbard Brook Valley, NH and has been the subject of numerous continuous limnological investigations since the early 1960s. This data set reports ice cover, ice in and ice out data beginning in 1968 and continuing through the present.
climate change, HBEF Mirror Lake Study, HBR, Hubbard Brook LTER, hydrology, ice, limnology.
Mirror Lake
West bounding coordinate: -71.701859
East bounding coordinate: -71.701859
North bounding coordinate: 43.943943
South bounding coordinate: 43.943943
Mirror Lake (area, 15 ha; max. depth, 11 m) is located within the Hubbard Brook Valley and has been the subject of numerous continuous limnological investigations since the early 1960s. Routine measurements of ice cover on Mirror Lake began in 1967; however the exact date of onset (ice in) in 1967 is uncertain so the data shown here begins in 1968. Dates for ice in and dissipation (ice out) of ice cover have been recorded using criteria that have been followed faithfully since the beginning of the study. The date of ice in is taken when >50% of the lake surface is covered with ice and remains covered. The date of ice out is taken when >50% of the lake surface is open water and the lake’s surface does not refreeze.
  • Likens, G.E. 2000. A long-term record of ice-cover for Mirror Lake, New Hampshire: effects of global warming?. Verhandlungen Internationale Vereinigung für theoretische und angewandte Limnologie 27:2765-2769.
  • Likens, G.E. 2011. Limnological measures related to climate change in the Hubbard Brook Valley, USA. Inland Waters 1(2):93-99.
Data Access Guidelines for Mirror Lake Ice Cover Data

We are happy to share these data on Mirror Lake Ice Cover. The public dissemination of these data that we have collected is a responsibility that we take very seriously. As stewards of these long-term data, our highest priorities are:

a. to maintain the integrity of these long-term data;

b. to allow adequate time for the analysis, quality assurance, and publication of results by principal investigators;

c. to acknowledge properly and responsibly the appropriate funding sources.

Therefore, it is HBES policy to make these data available on this web page two years after the date of collection. Also, in sharing these data with users like yourself, we ask that you adhere to the following guidelines as a matter of common courtesy and ethical responsibility:

1. Please inform us in advance of your interest and plans for use of these data (

2. The sources of funding used to collect these data must be acknowledged properly. We will provide the appropriate information when we learn what data are being used.

3. We would like to review any manuscripts that utilize extensive amounts (e.g. multiple years) of these data. If data use is extensive, or if these data have not been published previously, it may be appropriate for us to be included as authors on publication that are generated given the additional requirements from us for analysis and interpretation.

Data Use Policy

The re-use of scientific data has the potential to greatly increase communication, collaboration and synthesis within and among disciplines, and thus is fostered, supported and encouraged. Permission to use this dataset is granted to the Data User free of charge subject to the following terms:

1) Acceptable use. Use of the dataset will be restricted to academic, research, government or other not-for-profit professional purposes.

2) Redistribution. The data and metadata are provided for use by the Data User. The Data User will not redistribute the original Data Set or metadata to others without the explicit permission of the Principal Investigator.

3) Citation. It is considered a matter of professional ethics to acknowledge the work of other scientists. Thus, the Data User will properly attribute the Data Set in any publications or in the metadata of any derived data products that were produced using the Data Set. Citation should take the following general form: Creator, Year of Data Publication, Title of Dataset, Publisher, Dataset identifier.

Citation example: Holmes, R.T. 2012. Bird Abundances at Hubbard Brook (1969-2010) and on three replicate plots (1986-2000) in the White Mountain National Forest. Durham, NH. Hubbard Brook Data Archive [Database]. (23 July 2012)

4) Acknowledgment: The Data User should acknowledge any institutional support or specific funding awards referenced in the metadata accompanying this dataset in any publications where the Data Set contributed to its content. Acknowledgments should identify the supporting party, the party that received the support, and any identifying information such as grant numbers.

Acknowledgment example: Data on [topic] were provided by [name of PI] on [date]. These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station, Newtown Square, PA. Significant funding for collection of these data was provided by [agency]-[grant number], [agency]-[grant number], etc.

5) Consultation and questions. Data users are strongly encouraged to consult with the Principal Investigator(s) who collected these data for further information. Also, when appropriate, Data Users should consider including the Principal Investigator as a collaborator and/or co-author in the use of these data.

6) Notification. The Data User will notify the Principal Investigator of any publication or derivative work based on the Data Set. The Data User will also provide the Principal Investigator and/or the administrator of the Hubbard Brook Ecosystem Study with a pdf or two reprints of any publication(s) resulting from use of the Data Set.

7) Disclaimer. While substantial efforts are made to ensure the accuracy of data and documentation contained in this Data Set, complete accuracy of data and metadata cannot be guaranteed. All data and metadata are made available "as is". The Data User holds all parties involved in the production or distribution of the Data Set harmless for damages resulting from its use or interpretation.

8) Terms of Agreement. By accepting this Data Set, the Data User agrees to abide by the terms of this agreement. The Data Owner shall have the right to terminate this agreement immediately by written notice upon the Data User's breach of, or non-compliance with, any of its terms. The Data User may be held responsible for any misuse that is caused or encouraged by the Data User's failure to abide by the terms of this agreement.


Information Manager, Hubbard Brook LTER
234 Mirror Lake Road
North Woodstock, NH 03262

Phone: (603) 726-8902

Data file: ml_ice.txt
Description: Mirror Lake Ice Cover
ColumnVariableDescriptionUnitsCoded?Missing value label
1WATER _YRWater year (e.g. Water year 1968 begins on June 1, 1968 and ends on May 31, 1969YYYYnnone
2YRS_COVEREDCalender years coverednoneynone
3ICE_COVERNumber of days the lake is covered with IceDDDnnone
4ICE_INIce in date (Day of Year, e.g. DOY 365=December 31, DOY 1=January 1, DOY 97=April 7, etc.)DDDnnone
5ICE_OUTIce out date (Day of Year, e.g. DOY 365=December 31, DOY 1=January 1, DOY 97=April 7, etc.)DDDnnone


Range of years (YYYY-YYYY)