Title

Dataset Authors 1

Name

Crawford, Alex

Type of Name

Personal

Email

alex.crawford@umanitoba.ca

Affiliation

Centre for Earth Observation Science - University of Manitoba

ORCID ID

0000-0003-1561-290X

ORCID

http://orcid.org/

Contributors 1

Name

Stroeve, Julienne

Role

ProjectLeader

Email

julienne.stroeve@umanitoba.ca

Affiliation

Centre for Earth Observation Science - University of Manitoba

ORCID ID

0000-0001-7316-8320

ORCID

http://orcid.org/

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Publications 1

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Online Resource

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Name

Multi-Model Means of Hudson Bay Sea Ice Thickness Phenology

Description

Multi-model means from 1920-2099 for continuous ice-free period (IFP), last retreat day (LRD) and first advance day (FAD) using either a delta-shift bias correction (BC) or weighted mean (WM). Three regions are used: Hudson Bay (including James Bay, but excluding Hudson Strait and Foxe Basin), western Hudson Bay, and southern Hudson Bay. The latter two regions are commonly used for dividing the polar bear population in Hudson Bay. (e.g., https://polarbearagreement.org/polar-bear-biology/population-distribution-and-trends) The bias correction is conducted by comparing the observational average of sea ice phenology from the 1979-2021 passive microwave record to the years in each model for which the temperature anomaly relative to 1850-1900 is in the same range as recorded by the Berkeley Earth surface temperature dataset. For each model simulation, the difference in average IFP, LRD, and FAD for those years sharing the same temperature anomaly range is considered the bias, and this bias is subtracted from all years of data before calculating a multi-model mean from the first ensemble member (replicate) of each model. The weighted mean has two factors. First, a model simulation receives more weight if it shows better performance (relative to the passive microwave record for sea ice phenology and the Berkeley Earth surface temperature record) for that same period 1979-2021. Second, model simulations that show more independence from other simulations also receive more weight. In this way, it is possible to use multiple simulations (up to 7) from each participating model. The bias-corrected mean uses 20 simulations total, whereas the weighted mean uses 49.

Format

CSV

Resource Category

data

Name

Standard Error for Hudson Bay Sea Ice Thickness Phenology

Description

Standard error for multi-model means from 1920-2099 for continuous ice-free period (IFP), last retreat day (LRD) and first advance day (FAD) using either a delta-shift bias correction (BC) or weighted mean (WM). Three regions are used: Hudson Bay (including James Bay, but excluding Hudson Strait and Foxe Basin), western Hudson Bay, and southern Hudson Bay. The latter two regions are commonly used for dividing the polar bear population in Hudson Bay. (e.g., https://polarbearagreement.org/polar-bear-biology/population-distribution-and-trends) The bias correction is conducted by comparing the observational average of sea ice phenology from the 1979-2021 passive microwave record to the years in each model for which the temperature anomaly relative to 1850-1900 is in the same range as recorded by the Berkeley Earth surface temperature dataset. For each model simulation, the difference in average IFP, LRD, and FAD for those years sharing the same temperature anomaly range is considered the bias, and this bias is subtracted from all years of data before calculating a multi-model mean from the first ensemble member (replicate) of each model. The weighted mean has two factors. First, a model simulation receives more weight if it shows better performance (relative to the passive microwave record for sea ice phenology and the Berkeley Earth surface temperature record) for that same period 1979-2021. Second, model simulations that show more independence from other simulations also receive more weight. In this way, it is possible to use multiple simulations (up to 7) from each participating model. The bias-corrected mean uses 20 simulations total, whereas the weighted mean uses 49.

Format

CSV

Resource Category

data

Name

Hudson Bay Sea Ice Thickness Phenology - Historical

Description

Regional averages from 1920-2013 (Historical experiment from CMIP6) for continuous ice-free period (IFP), last retreat day (LRD) and first advance day (FAD) using either a delta-shift bias correction (BC) or weighted mean (WM). Three regions are used: Hudson Bay (including James Bay, but excluding Hudson Strait and Foxe Basin), western Hudson Bay, and southern Hudson Bay. The latter two regions are commonly used for dividing the polar bear population in Hudson Bay. (e.g., https://polarbearagreement.org/polar-bear-biology/population-distribution-and-trends)

Format

ZIP

Resource Category

data

Name

Hudson Bay Sea Ice Thickness Phenology - SSP585

Description

Regional averages from 2015-2099 (SSP585 experiment of CMIP6) for continuous ice-free period (IFP), last retreat day (LRD) and first advance day (FAD) using either a delta-shift bias correction (BC) or weighted mean (WM). Three regions are used: Hudson Bay (including James Bay, but excluding Hudson Strait and Foxe Basin), western Hudson Bay, and southern Hudson Bay. The latter two regions are commonly used for dividing the polar bear population in Hudson Bay. (e.g., https://polarbearagreement.org/polar-bear-biology/population-distribution-and-trends).

Format

ZIP

Resource Category

data

Name

Bias-corrected Multi-Model Average Grids

Description

The continuous ice-covered period (cip), advance day (fad), and retreat day (lrd) are defined using a sea ice thickness threshold of 10 cm. Each "year" is from September 1, Year 1 to August 31, Year 2 and dates are given as units of "days starting January 1 of Year 1". Original data source is 20 simulations from the historical and shared socioeconomic pathway 5-8.5 (ssp585) experiments from the Coupled Model Intercomparison Project version 6 (CMIP6). This thickness phenology for each model simulation (one simulation per model) was bias-corrected relative to average phenology derived from Bootstrap and NASA Team algorithms applied to passive microwave data for the period 1979-2021. For each model, the average modelled ice-covered period for years in which the temperature anomaly relative to 1850-1900 fell within the range observed in the Berkeley Earth Surface Temperature record for 1979-2021 was compared to the satellite observations. The difference was used as a bias adjustment, applied to all years. Next, an equally weighted multi-model mean was calculated for each 0.5°C global temperature anomaly bin (i.e., tanom = "1°C" means 0.5°C ≤ T' < 1.5°C).

Format

NetCDF

Resource Category

data

Name

Weighted Multi-Model Average Grids

Description

The continuous ice-covered period (cip), advance day (fad), and retreat day (lrd) are defined using a sea ice thickness threshold of 10 cm. Each "year" is from September 1, Year 1 to August 31, Year 2 and dates are given as units of "days starting January 1 of Year 1". Original data source is 49 simulations from the historical and shared socioeconomic pathway 5-8.5 (ssp585) experiments from the 20 models participating in the Coupled Model Intercomparison Project version 6 (CMIP6). A weighted average of the simulations was calculated for each 0.5°C global temperature anomaly bin (i.e., tanom = "1°C" means 0.5°C ≤ T' < 1.5°C). Weights were determined using a balance of model performance and independence, following the general framework of Knutti et al. (2017; https://doi.org/10.1002/2016gl072012). "Performance" was assessed by comparing modelled sea ice and temperature variables to observed values. More specifically, the compared variables were the averages and trends of sea ice retreat and advance, the ice-free period, and regional 2-m air temperature over western and southern sectors of Hudson Bay for the period 1979-2021. For sea ice, the observational reference was the average phenology derived from Bootstrap and NASA Team algorithms applied to passive microwave data. For temperature, the Berkeley Earth Surface Temperature dataset was used. The weighting parameters were sigma_D = 0.49 and sigma_S = 0.50.

Format

NetCDF

Resource Category

data