AGU17 Search “piomas”
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https://agu.confex.com/agu/fm17/meetingapp.cgi/SearchResults/0GC43J-04 PIOMAS-20C: Variability of Arctic sea ice thickness and volume over the 20th Century.
Axel J B Schweiger UW-APL
Changes in Arctic sea ice are a fingerprint of natural and anthropogenic climate change. The dominant signal in sea ice variability from 1979 to the present is the reduction of sea ice extent, area and thickness. Prior to 1979, the state of our knowledge about sea ice variability is limited to information about sea ice extent and concentration assembled mostly from shipping logs and very little is known about the variability of sea ice thickness and total sea ice volume.
Here we use the Panarctic Ice and Ocean Modelling and Assimilation system (PIOMAS) to generate a sea ice reanalysis from 1900 to 2010 (PIOMAS-20C). PIOMAS-20C is generated by forcing PIOMAS with atmospheric reanalysis data from the ERA-20C project. We present initial results that include validation of atmospheric forcing parameters over sea ice from the ERA20C project and sea ice thickness from PIOMAS-20C.
The PIOMAS-20C sea ice thickness is generally in
good agreement with available observations before and after 1979. We specifically investigate patterns of sea ice thickness and volume variability in the early 20th century and compare them with changes over the more recent period.
C33C-1205 Seasonal evolution of the Arctic marginal ice zone and its power-law obeying floe size distribution
Jinlun Zhang UW-APL
A thickness, floe size, and enthalpy distribution (TFED) sea ice model, implemented numerically into the Pan-arctic Ice–Ocean Modeling and Assimilation System (PIOMAS), is used to investigate the seasonal evolution of the Arctic marginal ice zone (MIZ) and its floe size distribution.
The TFED sea ice model, by coupling the Zhang et al. [2015] sea ice floe size distribution (FSD) theory with the Thorndike et al. [1975] ice thickness distribution (ITD) theory, simulates 12-category FSD and ITD explicitly and jointly. A range of ice thickness and floe size observations were used for model calibration and validation. The model creates FSDs that generally obey a power law or upper truncated power law, as observed by satellites and aerial surveys.
In this study, we will examine the role of ice fragmentation and lateral melting in altering FSDs in the Arctic MIZ. We will also investigate how changes in FSD impact the seasonal evolution of the MIZ by modifying the thermodynamic processes.
C21B-1119 Winter Arctic sea ice growth: current variability and projections for the coming decades
Alek Petty
Arctic sea ice increases in both extent and thickness during the cold winter months (~October to May). Winter sea ice growth is an important factor controlling ocean ventilation and winter water/deep water formation, as well as determining the state and vulnerability of the sea ice pack before the melt season begins. Key questions for the Arctic community thus include: (i) what is the current magnitude and variability of winter Arctic sea ice growth and (ii) how might this change in a warming Arctic climate?
To address (i), our
current best guess of pan-Arctic sea ice thickness, and thus volume,
comes from satellite altimetry observations, e.g. from ESA's CryoSat-2 satellite. A significant source of uncertainty in these data come from poor knowledge of the overlying snow depth.
Here we present new estimates of winter sea ice thickness from CryoSat-2 using snow depths from a simple snow model forced by reanalyses and satellite-derived ice drift estimates, combined with snow depth estimates from NASA's Operation IceBridge.
To address (ii), we use data from the Community Earth System Model's Large Ensemble Project, to explore sea ice volume and growth variability, and how this variability might change over the coming decades. We compare and contrast the model simulations to observations and the PIOMAS ice-ocean model (over recent years/decades). The combination of model and observational analysis provide novel insight into Arctic sea ice volume variability
C33B-1201 The Impact of Moisture Intrusions from Lower Latitudes on Arctic Net Surface Radiative Fluxes and Sea Ice Growth in Fall and Winter
Bradley M Hegyi
The fall and winter seasons mark an important period in the evolution of Arctic sea ice, where energy is transferred away from the surface to facilitate the cooling of the surface and the growth of Arctic sea ice extent and thickness.
Climatologically, these seasons are characterized by distinct periods of increased and reduced surface cooling and sea ice growth. Periods of reduced sea ice growth and surface cooling are associated with
cloudy conditions and the transport of warm and moist air from lower latitudes, termed
moisture intrusions.
In the research presented, we explore the regional and Arctic-wide impact of moisture intrusions on the surface net radiative fluxes and sea ice growth for each fall and winter season from 2000/01-2015/16, utilizing MERRA2 reanalysis data, PIOMAS sea ice thickness data, and daily CERES radiative flux data.
Consistent with previous studies, we find that positive anomalies in downwelling longwave surface flux are associated with increased temperature and water vapor content in the atmospheric column contained within the moisture intrusions.
Interestingly, there are periods of increased downwelling LW flux anomalies that persist for one week or longer (i.e. longer than synoptic timescales) that are associated with
persistent poleward flux of warm, moist air from lower latitudes. These persistent anomalies significantly reduce the regional growth of Arctic sea ice, and may in part explain the inter-annual variability of fall and winter Arctic sea ice growth.
C21D-1144: Anomalous circulation in the Pacific sector of the Arctic Ocean in July-December 2008
Gleb Panteleev
Variability of the mean summer-fall ocean state in the Pacific Sector of the Arctic Ocean (PSAO) is studied using a dynamically constrained synthesis (4Dvar) of historical in situ observations collected during 1972 to 2008. Specifically, the oceanic response to the cyclonic (1989-1996) and anticyclonic (1972-1978, 1997-2006) phases o f the Arctic Ocean Oscillation (AOO) is assessed for the purpose of quantitatively comparing the 2008 circulation pattern that followed the 2007 ice cover minimum.
It is shown that the PSAO circulation during July-December of 2008 was characterized by a pronounced negative Sea Surface Height (SSH) anomaly along theEurasian shelf break, which caused a significant decline of the transport in the Atlantic Water (AW) inflow region into the PSAO and increased the sea level difference between the Bering and Chukchi Seas. This anomaly could be one of the reasons for the observed amplification of the Bering Strait transport carrying fresh Pacific Waters into the PSAO.
Lagrangian analysis of the optimized solution suggests that the freshwater (FW) accumulation in the Beaufort Gyre has a negligible contribution from the East Siberian Sea and is likely caused by the enhanced FW export from the region north of the Canadian Archipelago/Greenland.The inverse modeling results are confirmed by validation against independent altimetry observations and in situ velocity data from NABOS moorings. It is also shown that presented results are in
significantly better agreement with the data than the output of the PIOMAS model run utilized as a first guess solution for the 4dVar analysis.