skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Direct Observations of Wave‐Sea Ice Interactions in the Antarctic Marginal Ice Zone
Abstract Wave energy propagating into the Antarctic marginal ice zone effects the quality and extent of the sea ice, and wave propagation is therefore an important factor for understanding and predicting changes in sea ice cover. Wave‐sea ice interactions are notoriously hard to model and in situ observations of wave activity in the Antarctic marginal ice zone are scarce, due to the extreme conditions of the region. Here, we provide new in situ data from two drifting Surface Wave Instrument Float with Tracking (SWIFT) buoys deployed in the Weddell Sea in the austral winter and spring of 2019. The buoy location ranges from open water to more than 200 km into the sea ice. We estimate the attenuation of swell with wave periods 8–18 s, and find an attenuation coefficientα = 4 · 10−6to 7 · 10−5 m−1in spring, and approximately five‐fold larger in winter. The attenuation coefficients show a power law frequency dependence, with power coefficient close to literature. The in situ data also shows a change in wave direction, where wave direction tends to be more perpendicular to the ice edge in sea ice compared to open water. A possible explanation for this might be a change in the dispersion relation caused by sea ice. These observations can help shed further light on the influence of sea ice on waves propagating into marginal ice zones, aiding development of coupled wave‐sea ice models.  more » « less
Award ID(s):
1853291
PAR ID:
10549205
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
AGU
Date Published:
Journal Name:
Journal of Geophysical Research: Oceans
Volume:
128
Issue:
10
ISSN:
2169-9275
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; (, Marine Ecology Progress Series)
    NA (Ed.)
    The Antarctic Peninsula marine ecosystem is highly productive, with large populations of commercially and ecologically important species including Antarctic krillEuphausia superba, Adélie penguinsPygoscelis adeliae, and crabeater sealsLobodon carcinophagus. The ecology of the peninsula is rapidly changing due to accelerating climate change and fishing pressure. Systematic ecosystem surveys have focused on austral spring and summer, leaving an information gap on winter ecosystem dynamics. Using data from 5 consecutive ecosystem surveys, we quantified the composition and distribution of winter predator communities and investigated the physical and biological influences on community structure. Seabirds and marine mammals clustered into 3 communities: an ice-associated community represented by Adélie penguins and crabeater seals; a diverse marginal ice zone community dominated by fur seals and several species of seabirds including 3 petrels, kelp gullsLarus dominicanus, and Antarctic ternsSterna vittata; and an open water community consisting of southern fulmarsFulmarus glacialoidesand 4 species of petrels. These communities were distributed along an environmental gradient ranging from ice-covered, cold, saline water to ice-free, warmer, and fresher water with greater chlorophyll concentrations. Predator communities were also associated with different communities of macrozooplankton: ice-associated predators with an extremely diverse assemblage of typically mesopelagic zooplankton; marginal ice zone predators with a community of large-bodied euphausiids (E. superba, E. crystallorophias); and open water predators with a community of small-bodied euphausiids (Thysanoessa macrura). Our synthesis of integrated winter predator and macrozooplankton communities relative to sea-ice concentration provides reference points for future ecosystem assessments within this rapidly changing region. 
    more » « less
  2. ; ; ; ; ; (, Geophysical Research Letters)
    Abstract Observations of ocean surface waves at three sites along the northern coast of Alaska show a strong correlation with seasonal sea ice patterns. In the winter, ice cover is complete, and waves are absent. In the spring and early summer, sea ice retreats regionally, but landfast ice persists near the coast. The landfast ice completely attenuates waves formed farther offshore in the open water, causing up to a two‐month delay in the onset of waves near shore. In autumn, landfast ice begins to reform, though the wave attenuation is only partial due to lower ice thickness compared to spring. The annual cycle in the observations is reproduced by the ERA5 reanalysis product, but the product does not resolve landfast ice. The resulting ERA5 bias in coastal wave exposure can be corrected by applying a higher‐resolution ice mask, and this has a significant effect on the long‐term trends inferred from ERA5. 
    more » « less
  3. ; ; ; ; ; ; ; ; (, Frontiers in Marine Science)
    The transition from winter to spring represents a major shift in the basal energy source for the Antarctic marine ecosystem from lipids and other sources of stored energy to sunlight. Because sea ice imposes a strong control on the transmission of sunlight into the water column during the polar spring, we hypothesized that the timing of the sea ice retreat influences the timing of the transition from stored energy to photosynthesis. To test the influence of sea ice on water column microbial energy utilization we took advantage of unique sea ice conditions in Arthur Harbor, an embayment near Palmer Station on the western Antarctic Peninsula, during the 2015 spring–summer seasonal transition. Over a 5-week period we sampled water from below land-fast sea ice, in the marginal ice zone at nearby Palmer Station B, and conducted an ice removal experiment with incubations of water collected below the land-fast ice. Whole-community metatranscriptomes were paired with lipidomics to better understand how lipid production and utilization was influenced by light conditions. We identified several different phytoplankton taxa that responded similarly to light by the number of genes up-regulated, and in the transcriptional complexity of this response. We applied a principal components analysis to these data to reduce their dimensionality, revealing that each of these taxa exhibited a strikingly different pattern of gene up-regulation. By correlating the changes in lipid concentration to the first principal component of log fold-change for each taxa we could make predictions about which taxa were associated with different changes in the community lipidome. We found that genes coding for the catabolism of triacylglycerol storage lipids were expressed early on in phytoplankton associated with aFragilariopsis kerguelensisreference transcriptome. Phytoplankton associated with aCorethron pennatumreference transcriptome occupied an adjacent niche, responding favorably to higher light conditions thanF. kerguelensis. Other diatom and dinoflagellate taxa had distinct transcriptional profiles and correlations to lipids, suggesting diverse ecological strategies during the polar winter–spring transition. 
    more » « less
  4. ; ; ; (, Paleoceanography and Paleoclimatology)
    Abstract Southern Ocean sea ice plays a central role in the oceanic meridional overturning circulation, transforming globally prevalent watermasses through surface buoyancy loss and gain. Buoyancy loss due to surface cooling and sea ice growth promotes the formation of bottom water that flows into the Atlantic, Indian, and Pacific basins, while buoyancy gain due to sea ice melt helps transform the returning deep flow into intermediate and mode waters. Because northward expansion of Southern Ocean sea ice during the Last Glacial Maximum (LGM; 19–23 kyr BP) may have enhanced deep ocean stratification and contributed to lower atmospheric CO2levels, reconstructions of sea ice extent are critical to understanding the LGM climate state. Here, we present a new sea ice proxy based on the18O/16O ratio of foraminifera (δ18Oc). In the seasonal sea ice zone, sea ice formation during austral winter creates a cold surface mixed layer that persists in the sub‐surface during spring and summer. The cold sub‐surface layer, known as winter water, sits above relatively warm deep water, creating an inverted temperature profile. The unique surface‐to‐deep temperature contrast is reflected in estimates of equilibrium δ18Oc, implying that paired analysis of planktonic and benthic foraminifera can be used to infer sea ice extent. To demonstrate the feasibility of the δ18Ocmethod, we present a compilation ofN. pachydermaandCibicidoidesspp. results from the Atlantic sector that yields an estimate of winter sea ice extent consistent with modern observations. 
    more » « less
  5. ; ; ; (, The Cryosphere)
    null (Ed.)
    Abstract. We investigate a case of ocean waves through a pack icecover captured by Sentinel-1A synthetic aperture radar (SAR) on 12 October 2015 in the Beaufort Sea. The study domain is 400 km by 300 km, adjacent to amarginal ice zone (MIZ). The wave spectra in this domain were reported in aprevious study (Stopa et al., 2018b). In that study, the authors divided thedomain into two regions delineated by the first appearance of leads (FAL)and reported a clear change of wave attenuation of the total energy betweenthe two regions. In the present study, we use the same dataset to study thespectral attenuation in the domain. According to the quality of SAR-retrieved wave spectrum, we focus on a range of wave numbers corresponding to9–15 s waves from the open-water dispersion relation. Wefirst determine the apparent attenuation rates of each wave number by pairingthe wave spectra from different locations. These attenuation rates slightlyincrease with increasing wave number before the FAL and become lower and moreuniform against wave number in thicker ice after the FAL. The spectralattenuation due to the ice effect is then extracted from the measuredapparent attenuation and used to calibrate two viscoelastic wave-in-icemodels. For the Wang and Shen (2010b) model, the calibrated equivalent shearmodulus and viscosity of the pack ice are roughly 1 order of magnitudegreater than that in grease and pancake ice reported in Cheng et al. (2017).These parameters obtained for the extended Fox and Squire model are muchgreater, as found in Mosig et al. (2015) using data from the Antarctic MIZ.This study shows a promising way of using remote-sensing data with largespatial coverage to conduct model calibration for various types of icecover.Highlights. Three key points: The spatial distribution of wave number and spectral attenuation in pack iceare analyzed from SAR-retrieved surface wave spectra. The spectral attenuation rate of 9–15 s waves varies around10−5 m2 s−1, with lower values in thicker semicontinuous ice fieldswith leads. The calibrated viscoelastic parameters are greater than those found inpancake ice. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email