DOI: 10.5061/dryad.n02v6wxb5
title: Brighter Ocean: Arctic sea ice solar partitioning

description: This dataset contains the partitioning of the surface downwelling
 radiative fluxes by the Arctic sea ice by reflection, absorption, and
 transmission. The dataset covers the period from 1984 to 2022 and was
 provided on 25 km resolution on the NSIDC EASE2 grid.
description: # Brighter Ocean: Arctic sea ice solar partitioning Dataset DOI:
 [10.5061/dryad.n02v6wxb5](https://doi.org/10.5061/dryad.n02v6wxb5) ##
 Description of the data and file structure Our focus is on the large-scale
 partitioning of the incident solar radiation between reflection to the
 atmosphere (albedo, *a*), absorption in the ice (absorptance, *A*) and
 transmission to the ocean (transmittance, *T*). These parameters were
 determined every day from 1984 to 2022 at every point on the Equal Area
 Scalable Earth 2.0 (EASE2) grid, within the sea ice extent boundary. The
 basis for the analysis relies on several satellite and model products.
 These include geophysical variables of shortwave radiation, surface melt
 and freeze onset dates, as well as sea ice concentration, age, and
 thickness. Sea ice albedo is estimated using a multiphase albedo evolution
 determined for first year ice (Perovich and Polashenski, 2012) and
 multiyear ice (Perovich et al., 2002; Light et al., 2022). Distinct albedo
 evolutions for first-year and multiyear sea ice are computed using Version
 4 of the EASE-grid Sea Ice Age product by Tschudi et al. (2019). The dates
 of melt and freeze-up book-end the Arctic melt season and govern the
 seasonal evolution of surface albedo of sea ice. For the onset dates of
 continuous melt and continuous freeze, we use passive microwave retrievals
 at 25-km resolution produced by Markus et al. (2009). The ice
 concentration is a key parameter in determining the solar partitioning. We
 use passive microwave retrievals from the NASA Bootstrap algorithm
 (Comiso, 1986), which are available in the NOAA/NSIDC Climate Data Record
 (Meier et al., 2021). The product is provided at daily 25-km gridded
 resolutions. In some instances, temporal gaps in the data exist due to
 inconsistent satellite coverage. Transmittance through the ice is defined
 by an exponential decay law of the form and corrected for the near
 infrared light absorbed by the snow and ice and not transmitted. The
 correction ratio is estimated to vary from about 0.55 for clear skies to
 0.62 for complete cloud cover. An average value of 0.58 is used in this
 study. The ice extinction coefficient for visible light. Based on field
 observations (Light et al., 2008, 2015), we use 1.0 m-1 for an ice cover
 dominated by bare ice (0.5 &lt; *a~i~* &lt; 0.7), 3.0 m-1 for a cover
 dominated by snow (*a~i~* &gt; 0.7), and 0.7 m-1 for an ice cover
 dominated by melt ponds (*a~i~* &lt; 0.5). *S*ea ice thickness and is
 determined using the simulated thickness from the Pan-Arctic Ice Ocean
 Modeling and Assimilation System (PIOMAS) (Zhang and Rothrock, 2003). ###
 Files and variables #### File: BO_EASE2_gridded_25km_YYYY.nc
 **Description:** for year YYYY. **Variables:**  dimensions: X = 263, Y =
 263, time=365 or 366. insol (time,Y,X): surface downwelling solar
 radiative flux sic (time,Y,X): sea ice concentration sith (time,Y,X): sea
 ice thickness iceage (time,Y,X): sea ice age emelt, efreeze, fmelt,
 ffreeze (Y,X): Early ('e')/full ('f') melt/freeze
 onset date, in day-of-year. alb_yyy (time,Y,X): ice albedo using albedo
 scheme yyy. The albedo scheme include MYI (using multi-year ice scheme),
 FYI (using first-year ice scheme), and AGE (combined multi-year and
 first-year albedo depending on ice age). h_xxx_yyy (time,Y,X): heat flux
 on xxx surface type using albedo scheme yyy, with unit of W/m^2^. The xxx
 surface types include nIC (assuming fully ice covered), ice (ice portion
 of the gridbox), ocn (open water portion of the gridbox). The yyy albedo
 scheme include MYI (using multi-year ice scheme), FYI (using first-year
 ice scheme), and AGE (combined multi-year and first-year albedo depending
 on ice age). An exemption is h_ocn_SIC, the heat input to the open water
 portion of the gridbox using the sea ice concentration. accu_h_xxx_yyy
 (time,Y,X): the accumulated heat input into the gridbox, with unit of
 MJ/m^2^. hthr_ice_xxx_KAPPA0 (time,Y,X): the heat through ice portion of
 the gridbox, using albedo scheme xxx and constant ice extinction
 coefficient kappa of 1, with unit of W/m^2^. hthr_ice_xxx_KAPPA_ALB
 (time,Y,X): the heat through ice portion of the gridbox, using albedo
 scheme xxx and ice extinction coefficient kappa depending on ice albedo
 value, with unit of W/m^2^. accu_hthr_ice_xxx_KAPPA0 (time,Y,X): the
 accumulated heat through ice portion of the gridbox, using albedo scheme
 xxx and constant ice extinction coefficient kappa of 1, with unit of
 MJ/m^2^. accu_hthr_ice_xxx_KAPPA_ALB (time,Y,X): the accumulated heat
 through ice portion of the gridbox, using albedo scheme xxx and ice
 extinction coefficient kappa depending on ice albedo value, with unit of
 MJ/m^2^. ## Code/software The software for processing and analyze this
 dataset is published on Zenodo:
 [10.5281/zenodo.17675721](https://doi.org/10.5281/zenodo.17675721) The
 developmental package is hosted o GitHub:
 [https://github.com/liuzheng-arctic/BrighterOcean](https://github.com/liuzheng-arctic/BrighterOcean)