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5 Climate-Change-Related Technical Issues Impacting U.S. Naval Operations
Pages 94-113

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From page 94...
... The chapter then discusses communication systems performance in polar regions, followed by an examination of current nautical products and systems; also discussed is the critical role of ice characterization in operational safety in Arctic navigation. The chapter concludes by discussing climate-changerelated antisubmarine warfare (ASW)
From page 95...
... GPS Performance Issues Global Positioning System satellite orbit inclinations are at 55° to optimize performance in temperate and tropical regions of high activity. This results in low satellite elevation angles in polar areas, with approximately 45° being the highest satellite elevation angle possible at the poles.
From page 96...
... Additionally, irregularities in electron density, known as scintillation effects, can lead to significant phase and amplitude fluctuations in GPS signals as they pass through the ionosphere. 1 For a more detailed discussion of GPS performance issues, see Dennis Milbert, 2009, "Improving Dilution of Precision," GPS World, November 1.
From page 97...
... 4 Possible Solutions to Address Arctic Navigation Challenges As explained above, GPS is an essential worldwide navigation aid that (due to ionospheric conditions and satellite geometry) provides slightly degraded service in the Arctic region, particularly increasing vertical navigation error with latitude 2 For a more detailed discussion of ionospheric effects, see John A
From page 98...
... -- constellations Russian system satellite geometry better due to higher inclination. MEO satellites Medium impact High impact Yes using WAAS signalsa Integrate GEO Low impact High impact Yes High-integrity GPS + LEO satellites (sidecar unit, augmentation system for WAAS backward (NRL R&D program)
From page 99...
... using new satellites at higher orbit inclinations to cover the polar regions or (2) augmenting the GPS signal by transmitting corrections from either land-based beacons or a high-latitude overhead presence (such as other satellite systems or long-persistence unmanned aerial vehicles [UAVs]
From page 100...
... communication systems, there is a high likelihood that a warming climate will ultimately increase the operational tempo in Arctic regions and thus the demands on communication systems to operate in a familiar fashion and with performance standards similar to those that the naval forces have trained with and become accustomed to. Today's U.S.
From page 101...
... It is not uncommon for Coast Guard operations at higher latitudes to depend on low-elevation communications to GEO satellites -- even if they require special positioning of the ship to gain favorable geometries -- as opposed to struggling with HF systems. Ionospheric disturbances of VHF voice and data communications are less intense than for HF bands, but they are still very problematic in the high Arctic (northward of 80° north latitude)
From page 102...
... 5-4 frequencies are minimally impacted by Arctic environmental phenomena, but the geometry imposed by the high-latitude antenna coverage is the key limitation. The two primary causes of over-the-horizon satellite communication degra dation are the increased atmospheric RF losses due to increased path length at low antenna elevation angles and increased system noise due to antenna beam interception of the warm Earth as opposed to the cold background of space.
From page 103...
... Ice Characterization and Arctic Navigation Knowledge of current ice conditions is crucial to safe maritime operations in the polar regions. The tri-agency Navy/NOAA/Coast Guard National Ice Center (NIC)
From page 104...
... Since seasonal ice is more prone to breaking up and creating dangerously dynamic ice floe conditions than is multiyear ice, augmentation of sea-ice coverage charts with ice thickness estimates would be very useful for maritime operations safety -- including surface, subsurface, and certain air operations. Similarly, near-real-time characterization of ice concentra tion and features in the marginal ice zones would greatly enhance operational safety.
From page 105...
... Ice type is correlated, though imperfectly, to ice thickness. SARs can also operate in cross track interferometry mode, which can make vertical height measurements of 1 meter resolution, depending on a number of system factors.
From page 106...
... Likewise, data on terrain elevation and bathymetry to support military operations and nautical charting are of low resolution and sparse in the Arctic. Moreover, while accurate ice coverage charts are available to guide surface navigation, reliable real-time ice characterization and maps in emergent Arctic transit routes are not.
From page 107...
... Additional support infrastructure must be established or restored to enable more effective ASW operations in that region, which will become an inevitable national imperative. Ocean acoustics are fundamental to submarine operations and antisubmarine warfare.
From page 108...
... Simply not enough is known about potential climate-change-related impacts on marine animals to make any predictions related to the noise environment, except that temperature and salinity changes will almost certainly lead to changes of habitat. Arctic Antisubmarine Warfare Operations The reduction in Arctic sea ice and the increased exploration accessibility to potential natural resources has already led to the Arctic nations posting overlapping and disputed claims of territory, as discussed in earlier chapters of this 17 The prediction codes model just the water column and not the atmosphere.
From page 109...
... Arctic Antisubmarine Warfare Arctic Ocean ASW is especially sensitive to the issues outlined above. Currently, virtually all knowledge of Arctic climatology is from submarine transits.
From page 110...
... This is being observed with the retreat of the seasonal Arctic sea ice. 21 In summary, there is a sparse data set, and the committee notes that it will need to be updated more frequently because of the more rapid changes at the polar latitudes.
From page 111...
... This makes identifying a target difficult. There are currently few ships in the Arctic, but warming may lead to increased maritime trade, more ships, and more difficulty in classification, although this will probably not reach the level of difficulty seen in sea lines of communica tion in the temperate oceans.24 Biologic noise, as well as that due to ice activity in the marginal ice zone, is very high and can aggravate classification efforts.
From page 112...
... FINDING 5.2a: Arctic ASW is difficult because of the complications of the environment -- the submarine and a source are typically in the section of the sound fixing and ranging (SOFAR) channel that has the most variability in sound speed.
From page 113...
... naval forces to conduct antisubmarine warfare (ASW) operations in the Arctic, the Department of the Navy should increase its submarine Arctic presence for train ing purposes, extend its supporting ASW oceanographic data infrastructure to the Arctic Ocean, and begin to conduct multiplatform ASW training exercises in the Arctic.


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