Understanding climate
for the benefit of society

A brief history of sea ice in the Nordic Seas

In this project we will synthesize research on long-term changes in sea ice in the Nordic Seas and adjacent areas.


The goal of the proposed effort “A brief history of sea ice in the Nordic Seas and adjacent areas – and its role in past, present and future climate change” is to produce the first comprehensive synthesis of long-term changes in sea ice in the Nordic Seas and adjacent areas that provides a past-present-future perspective, as well as clarifies insights into mechanisms and climate dynamics related to sea ice variability.

The foundation of the synthesis will be sea-ice reconstructions from past and ongoing Bjerknes projects and other pertinent paleo data. These will be complemented by the latest Coupled Model Intercomparison Project (CMIP6) projections for sea ice in the 21st century – see figure.

We will leverage recent analysis of sea-ice processes in simulations to evaluate sea-ice projections. This synthesis effort will not be merely a review, but rather a hands-on data synthesis resulting in valueadded advancement of the state-of-the-art, such as previous Bjerknes syntheses by Smedsrud et al. (2013) and Eldevik et al. (2014). There are remarkably few publications that have reviewed or synthesized the history of sea ice. Aside from overviews of sea-ice proxy methods, a standard reference is Polyak et al. (2010), with ~300 citations. Polyak et al. (2010) provide a reasonably thorough overview of sea ice reconstructions and past changes in sea ice in the Arctic.

However, there are several aspects regarding Polyak et al. (2010) that we will advance upon:

  1. We will produce a data synthesis rather than a review (Polyak et al., 2010), to understand the mechanisms and climate dynamics, here incorporating elements of the Margit Simon’s suggested synthesis, e.g., sea ice-climate linkages during glacial states and glacial-interglacial changes.
  2. We will include substantially more data records especially from the Nordic Seas and adjacent regions, to focus the scope on the dynamically important Atlantic Arctic, a confluence of temperate and ice-laden polar currents including the Earth’s largest sea ice and freshwater pathway, the East Greenland Current system.
  3. We will also take advantage of significant advances in recently developed new proxies, e.g., seaice biomarker proxy IP25 and ancient DNA (aDNA) in marine sediments, coralline algae as a seaice proxy, and ice-core chemistry from the Renland ice cap as an indicator of Greenland Sea ice – all featured in recent and ongoing Bjerknes projects (PEGSIE, ice2ice, and ERC-AGENSI).
  4. We will not be restricted to the past, but also evaluate the present and future of sea ice. The research community needs a comprehensive treatment of sea ice in the climate system as inferred from changes in past warm periods and across major climate transitions. The synthesis will span from deep time (e.g., Pliocene warm period), through the Quaternary glacial–interglacial transitions, and the Holocene, focused on the Holocene Climatic Optimum and the past millennium, which includes major climate transitions such as Medieval Climate Anomaly–Little Ice Age (LIA), variability within the LIA, and the LIA to the 20th century transition. Having synthesized past sea ice, we will then assess the present state of the sea ice compared to during previous warm periods, e.g., Pliocene, Holocene Climate Optimum (HCO), and MCA. Moreover, beyond providing a paleo perspective on climate change, it is natural to synthesize the state-of-the-art on the transition to future changes in sea ice – here addressing present-day changes and future projections for the Anthropocene through synthesis of CMIP6 model results.


This data synthesis will result in a benchmark paper in a high-visibility journal, Reviews of Geophysics, strengthening the profile of the Bjerknes Centre as a world leader on sea ice in the Nordic Seas and Arctic. This is an appropriately ambitious but fully realistic effort, given the strength of expertise and experience in past and ongoing projects – some of which (e.g., EastGreen and ULTRAMAR) involve data synthesis – and the concentration of resources for the core team of authors of the proposed paper. The lead author has demonstrated experience in producing synthesis papers, e.g., Drinkwater et al. (2014), Miles et al. (2014) and Miles et al. (2019, in review)

Leader: Martin Miles